http://www.kolab.org - A great Exchange Replacement!
http://www.gentoo.org - The best distribution out there (ok, its my opinion)
http://desktop.vidalinux.com - gentoo with installer
http://www.selfhtml.org - SelHtml the best html and javascript reference existing
http://www.iprcom.com/papers/pagerank/ - ever wondered how the google pagerank works???
http://www.digilife.be/quickreferences/quickrefs.htm - Quick References...

http://www.ctrlaltdel-online.com - One of the best internet Comic out there
http://www.knightsdivine.de - It's a browser based massive online strategy game, but one of the best I found (plus it's tick based so you dont sit in front of your screen waiting for an att or deff...) oh, it's in german
http://www.xgenstudios.com/play/castle/ - Throw little people who want to destroy your castle around :)
http://www.network-science.de/ascii/ - an asciiart generator, quite a lot of fun
http://www.stumbleupon.com - Install it and you never have a boring moment (or get any work done for a week)

http://www.gmiatlich.com - Something I do during my free time, organizing parties :)
http://www.corinis.com - My company (Tnks for the Cms)
http://www.samtex.net - Samtex (It's family, but I still call him a friend :P)