It's quite some time since I've had the time to update this list... sorry for that! :D
Here's the "most wanted"-list in the world of mac,
I'll do my best to continuously update it with new apps.
Hope you find this useful, if not, or if you know something I don't, don't hesitate to contact me...
* - Apple Design Award winner
Customizing your OS
Cocktail - Adds more features in System Preferences
TinkerTool - Unveils hidden system settings
Dragthing - Dock alternative. Very customizable
Overflow - Quick access to whatever you please
FILERUN - Finder alternative
3D Space VFS - Cool 3D file browser
Path Finder - Powerful Finder alternative
ShapeShifter - Give your GUI a facelift
Dockscrew - Make dock 3d in Leopard
ClearDock - Makes the Dock transparent
TransparentDock - Tweak your dock
Candybar - Customize all system icons
MenuCalendarClock - Custom time display for the menubar.
Meteorologist - Shows current weather in the menubar. Nicely integrated into iCal
Coconut battery - Custom battery capacity display
Menumeters - realtime menubar system stats display
Aurora - Alarm clock app that plays music
kisMac - wireless sniffer
Sleepless - Control what parts of your computer go to sleep
Jiggler - Keep your Mac from going to sleep
Virtue Desktop - Adds virtual external displays
SlapBook - Slap ypur mac to change desktop, works with Virtue Desktop
Desktop Manager - Adds virtual external displays. Similar to Spaces
Launchbar - App launcher
Quicksilver - App launcher (to say the least), Great!!
Butler - App launcher
Growl - Cool app alert
Letterbox - plugin for Mail which optimizes the app for widescreen displays
Windowshade X - Allows OS9 style collapsible windows
Mira - Customize your Apple remote
Airfoil - Use AirTunes w/ any app
Linotype Font Explorer X - Font activation & management
Typeset - Great font app for preview and sorting.
FontAgent Pro - Font manager, great!
TextMate - Powerful text editor
WriteRoom - Nice typewriting app
TextExpander - Makes shortcuts for typing, great!
Backlight - Use your screen saver as a wallpaper
Inquisitor - Searchplugin for Safari
Saft - Great plugin for Safari
Cunning Fox - Stop and continue running applications, CPU controller.
Stop App - Stop and continue apps for better CPU performance.
iFreeMem - Refresh and release inactive memory
Witch - Great window manager
rooSwitch - Create different settings for your apps
Nocturne - Night vision mode on your mac
Telekinesis - Control your mac with your iPhone
Soundflower - system extension for passing audio between apps
AppFresh - Keeps your apps up to date
Parallels Desktop - Virtual PC on your mac
CrossOver - Runs Windows application on your mac
rooSwitch - mabnage different profiles for applications
SwitchResX - Manage resolutions of all your monitors
2DOrNot2D - Make Leopard-dock 2D
A Better Finder Rename - File renaming app
Dockless - Hide/show dock-icon of running apps
Deep Freeze Mac - If something, anything goes wrong, use DFM, Great!
iStat menus - Advanced system monitor in menubar
Quay - Makes hierarchical menus to stacks in Leopard
Imaging
SketchUp - Cool 3D sketching software
MacOsaix - Make a photo mosaic out of photos
Slides! - Quick and easy full screen picture viewer
iView MediaPro - Great photo organizer/view. iPhoto alternative
Adobe Lightroom - Photo organizer/viewer/editor.
Aperture - Professional image editing, Great!!
Photo Mechanic - Photo organizer/view.
Xee - Fast image viewer/browser
Lineform* - Graphic design/drawing app
PhotoPresenter* - Slideshow maker
FotoMagico* - Slideshow maker
Modo* - 3D modeling
Blender* - 3D modeling
Photomatix - Great for HDR-images
Calico - Makes panorama photos
Image Tricks - Make your photos funny
Pixen - Pixel editor
OsiriX* - Medical imaging software
Seashore - Cocoa-based image editor
Paparazzi! - take screenshots of webpages
Picturesque* - Makes your photos gorgeous
Naked Light - Groundbreaking image editor
Photon - Photo browser/organizer
Pixelmator - Beautiful and useful image editor, Great!
Opacity - Drawing vector
Drawit - Nice app for vector drawing
Piclens - Amazingly nice plugin for Safari and Firefox, for viewing images.
Jade - Easy to use image editor.
iTunes
Sizzling Keys - Control iTunes anywhere
X-Tunes - Control iTunes anywhere w/ keyboard shortcut
Coverflow - Browses music via album covers in a jukebox
iVisualization - Visualizer for iTunes
Eyephedrin - Visualizer for iTunes
Corripio - Gets artwork and lyrics and adds them your songs ID tag
Senuti - Copies songs from iPod to iTunes
YamiPod - iPod file extractor
iScrobbler - Submits played iTunes tracked to Last.fm
iEatBrainz - Correctly names downloaded iTunes tracks
iPodDisk - Take songs off your iPod using the Finder
ourTunes - download songs from iTunes libraries on your network
Blue Coconut - like ourTunes, but only one user at a time since it's integrated into iTunes
Synergy - Great iTunes companion.
Coversutra - Ultimate companion for iTunes, GREAT!
Volume Logic - plugin for iTunes that enhances sound quality
Awaken - Wake up to your favourite tunes
Tunatic - Song search engine based on sound. Great!
SRS iWOW - audio enhancer, Great!
iTunes-LAME - LAME MP3 encoder, Great!
iTunify - Control over your iTunes library
Sing that iTune - widget that fetches lyrics and artwork and saves into songs
Harmonic - widget for fetching lyrics
M-Beat - iTunes companion application
Messengers
Adium - Super customizable. Supports many clients.
Mercury Messenger - Good messenger w/ webcam feature
Skype - VoIP (talk via internet for free)
Chax - iChat upgrades (a must for iChat users)
Colloquy - IRC client
Gizmo Project - VoIP
Chax - iChat addon with many nice features
Audio
Audacity - Music editing software
Audio Hijack - Record audio output from any app
WireTap Pro - Record speaker audio output
PandoraMan - Great app for listening to Pandora online music radio
Voice Candy - Fun program to change and modify your voice
Max - Convert and play Flac (lossless audio)
Fission - Lossless audio editing
Play - Audioplayer that supports FLAC, Ogg Vorbis and many more formats
Mixmeister Fusion - DJ mixing
DJay - Audio mixing app
AudialHub - Universial Audio converter, great.
Video
Flip4Mac - Plays .wmv files in Quicktime (a must)
FFMPEGX - Converts video files (can be tricky)
VLC - Great video player. Plays almost everything
DivX Doctor / 3iVx - Converts .avi to .mov
Dvd2oneX - DVD compression
Delivious Library - DVD library with reviews!
Handbrake - Rips DVDs
MacTheRipper - Rips DVDs
DVD Ripper for Mac - well, I guess... it can be used for ripping...
iShowU - Records video of your screen for learning/demoing purposes
Screencast - Records video of your screen.
Snapz Pro X - Records anything on your screen
Perian - Quicktime component that adds support for many popular formats
VisualHub - Great universal video converter
iSquint - iPod video converter
Joost - The future TV, internet TV
Zattoo - Live TV on your mac
MPlayer OSX - Video player that plays almost everything
NicePlayer - QuickTime based video player
RipIt - Rip DVD's
Web
Camino - Browser
OmniWeb - Browser
Flock - Browser
Sunrise - Browser
Opera - Browser
iCab - Browser
BumperCar - Web browser for kids
AcidSearch - Add any search engine to Safari's Google toolbar
Shiira - Lets you expose like tabbed browsing and ]s with web pages
Times - Beautiful RSS reader
Newsfire - Great RSS reader
NetNewswire - RSS reader
Vienna - Free RSS/Atom newsreader
Coda* - web development
cssedit* - website creation
Sandvox - website creation
Pathway - Wikipedia-browser
RapidWeaver - great web design software
Domainer - Domain and website manager
DomainTracker - Domain organizer
Google Sitemap Automator - Creates sitemap and notifies search engines
SiteSucker - Downloads websites, Great!
Web Snapper - Great for making pdf's from a webpage.
FTP
Flow - Great app
Games
KiBG - Gameboy emulator
VBA - GBA emulator
Stepmania - DDR on your computer
Utranium
Quinn - Tetris for your Mac
Open Arena - Quake-like game
Frenzic - Puzzle game
Freeverse.com has quite a list over free mac games
Tangle - Puzzle game
P2P
Shakespeer - DC++ client
Acquisition - P2P/BitTorrent client
BitTorrent - BitTorrent client
Poisoned - P2P
Transmission - BitTorrent client
Xtorrent - BitTorrent client
Azureus - Advanced BitTorrent client
Tracker Spy - keep track of what is open for signup
School
SchoolHouse - Great schoolwork organizer
iProcrastinate - Schoolwork organizer
iFlash - virtual flashcards
ProVoc - Foreign language learning aid
GraphClick* - Retrieve data from images or movies
Genius - Excellent app for learning
Organization
Delicious Library* - Make a database of your dvds, cds, books, games, etc.
DVDpedia - Great app for your DVD collection
iPSP - PSP management
Cashbox - Money management
iSale* - Manage your eBay auctions
Cha-Ching - easy to use money management
iBank - Complete Financial manager
Cents - Nice little app for you small spendings.
Papers - The library of science, manage articles
Mori - Record and organize your thoughts/notes
TaskPaper - "Getting Things Done" application
Curio - "Organize your mind"-app
MindManager - "Organize your mind"-app
iSticky - Memo assistant
Connoisseur - Cookbook-app that manages your recipes and more
Maintenance
Drive Genius - Maintain, manage and optimize
App Zapper - Handy app removal app
Blue Harvest - Removes pesky "._" files that only Windows users see
Littlesnitch - Detects/alerts/blocks/allows apps from accessing the network/internet
iClean - Clears history, cookies, cache, etc.
Disk Warrior - Disk maintenance/repair utility
TechTool Pro - Disk maintenance/repair utility
iWipe - Secure file/disk eraser
Xslimmer - slim your apps for PowerPC or Intel
iDefrag - Defragment you mac
OnyX - Clean up your mac
Maintenance - System cleaning and maintenance
WhatSize - See what takes up space on your mac
Disk Inventory X - See what takes up space on your mac
SuperDuper! - backup app, Great!
Programming
BBEdit - Great coding app
<oXygen/> - excellent XML app
Vim - GUI for Vi editor
Open Terminal - Open terminal in Finder
Taco HTML edit - HTML editor
Nvu - a more advanced iWeb-type webpage maker
Xcode - application development kit
Araelium Edit - Software development app
Unity - Game development tool
Other
Google Earth - Cool mapping app
Toast Titanium - Great CD/DVD burning/copying app
Disco - Megacool burning app with smoke. Great!
Comic Life - Make a comic of your life
R-name - Quick and simple batch rename
Salling Clicker - Control your computer thru a bluetooth pda phone. Great iTunes remote
Trail Runner - Maps your runs and loads them to the Nike+iPod setup.
Pastor - store all your passwords, serials and website logins safely
1Password - great app for managing all your passwords and serials
PDFKey Pro - Locks/unlocks pdf files
Undercover - very helpful if your mac gets stolen! Great!
Pzizz - Sleep/Energizer app, Great! It actually works!
Exces - File encryption made easy
Checkout - Run your shop/business from your mac
Celtx - Media pre-production and collaboration tool
BitClamp - Data encryption tool, Great!
Wallet - Organize your passwords, serials, credit cards etc., Great!
RemoteBuddy - Amazing tool to control your mac with Apple remote
Cool Useless Apps
iAlertU - Uses remote like a car alarm remote
MegaMan Effect - Each app gets a MegaMan style intro
MacSaber - Makes lightsaber noises when you move your laptop
Seizmac - Motion sensor detects...earthquakes??
Smackbook - Change desktops via smacking
Eyeballs - Eyeballs in the menubar follow your cursor
Nice Widgets
iClip lite - Really handy clipboard widgets
iStat Nano - System stats
iStat Pro - Ultimate system-stats-monitoring-widget
Harmonic - iTunes lyrics. Works better than SingThatiTune!
Share Switch - Turn File Sharing on/off. Great GUI.
Dashflix - Netflix manager
Screenshot Plus - Custom screen capture methods
Lost Widget - Every 108 minutes the button MUST be pushed!
The BART Widget* - Trip planner for the BART train system in California
PEMDAS - advanced and useful calculator
* - Apple Design Award winner