Just a few of the top of my head:
Easy to use Backup Tool: duplicati.com
For Email's: mozilla.org/en-US/thunderbird
For RSS Feeds: feedreader.com
Notepad replacement with lots and lots of features: notepad-plus-plus.org
For moving huge files: codesector.com/teracopy
For Music: winamp.com
For Videos: videolan.org/vlc
IM Client with a lot of customizeability and features: miranda-im.org
Awesome browser: coolnovo.com
With Windows8:
This get's rid of the volume rocker and replaces it with a highly customizeable one:
http://irzyxa.deviantart.com/art/Volume2-version-1-1-3-247-Release-340146840
Windows 7 like Startmenu for Windows 8: startisback.com
VSS with Windows 8: shadowexplorer.com