Automatic RSS + Bittorrent downloading
Zoom and OS X app fullscreen
A smarter default browser for OS X
Firefox 3 PDF Viewer Plugin
Manage multiple iTunes libraries
Mount remote filesystems over ssh for use in all osx apps
If your Entourage <-> iCal sync seems off by a set number of hours, this is probably the problem.
Automating security when away from home
(body)
Syncs OS X system proxy settings to Firefox automatically
Free up disk space from other localizations / platforms