This is a good thread!
www.pandora.com - My husband introduced me to this online radio and i use it daily ever since. Try it! You can create your own station with your favorite band/artist.
For MAC users:
www.adiumx.com - Connect to multiple IM accounts simultaneously in a single application, including: AOL IM, MSN, and Jabber. Beautiful, and more. They don't support Skype. I hope they will soon.
www.openoffice.org - A full-featured, office suite compatible with Microsoft Word, Powerpoint, and Excel.
www.cyberduck.ch - open source FTP
Here's the website if you want to check out more Open Source for MAC:
www.opensourcemac.org. I've only tried a few of them and they work good.