Meteorologist Displays a weather forecast in your menu bar.
RBrowser FTP, SFTP and SSH browser that also transfers the ressource fork of your files.
KISMac Wardr... err, network analysis tool with some nice features.
Fugu Another SFTP, SCP client.
Carbon Copy Cloner Burn bootable backups of your HDD.
Cocoa Gestures Implements mouse gestures in Cocoa programs.
iCab Much too unknown webbrowser with integrated HTML validator.
HandBrake DVD to MPEG-4 ripper.
Quicksilver Launch and operate applications with a single keystroke.
iAlertU Advanced anti theft utility for Mac Laptops.
Virtue Desktops Virtual desktops utility.
Teleport Those who use more than one Mac at the same time with only one mouse can use this "teleportation device" for the mouse pointer.
MyTunesRSS (Password protected) access to your iTunes library through any network.
Max Open source audio converter with Aqua interface.
iSquint iPod and PSP compatible video converter.
PodTube From YouTube to iTunes/iPod in one click.
3vix D4 Codec pack with 3ivx, DivX and XviD support.
ColdCompress .tar.gz generator.
ffmpegX Powerful video converter, shareware.
Wireless Host Monitor Check who's logged in your Airport WLAN.
Hugin OSX Open source panorama stitcher. (Requires another OS plugin for smooth transitions)
MP3 Trimmer Lossless cutting of MP3s, fade-in and fade-out inclusive.
QTAmateur Adds the fullscreen feature to QuickTime. Sometimes VLC isn't good enough.
X-Chat Aqua Another IRC client.
Some useful software collections:
[*]
The Underdogs Mac abandonware games. Attention: OS X/PPC Macs need classic environment installed to run them. OS X/x86 Macs need to get OS 9 running in another way. It's not that simple but instructions can be found
here.
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Mac Game Files Self explanatory.
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Softpedia
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MacUpdate
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OS X Downloads Apple itself. Great Dashboard Widget collection.
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VersionTracker My favorite.