Lifehacker, tips and downloads for getting things done
http://lifehacker.com

Open Source Mac
http://www.opensourcemac.org

GNU/Linux Essentials (Debian/Ubuntu/Fedora/Arch):
I am working on this list, please wait:)

Open Source Windows
http://opensourcewindows.org/

Best Software for Mac OS X (OSX)
http://www.bestmacsoftware.org

The Best Software for Windows
http://www.bestwindowssoftware.org

The best free software for Windows and Mac
http://www.bestfreesoftwarelist.com

Portable software for USB drives (Try it, make all your apps portable is good, for Windows Users only.)
http://portableapps.com