I thought it might be good to have a thread containing essential applications for OSX. It'll help me and maybe others to make the move from Windows easier.
FTP - Cyberduck - http://cyberduck.ch/ - Free
Video Player - VLC - http://www.videolan.org/vlc/ - Free
IRC - Colloquy - http://colloquy.info/ - Free
IM - Adium - http://www.adiumx.com/ - Free
Anti Theft - iAlertU - http://www.slappingturtle.com/home/?p=12 - Free (beta)
FTP - Cyberduck - http://cyberduck.ch/ - Free
Video Player - VLC - http://www.videolan.org/vlc/ - Free
IRC - Colloquy - http://colloquy.info/ - Free
IM - Adium - http://www.adiumx.com/ - Free
Anti Theft - iAlertU - http://www.slappingturtle.com/home/?p=12 - Free (beta)
I've just tried out Delicious Library! How cool is this program 
It basically stores a library of your cds/dvds/books/etc... but you can use your iSight to scan the barcodes, and it works very well.