1.Firefox Web Browser-
Google Chrome is terrific and Opera is fun but I keep coming back to Firefox.
2.Google Picasa -
Fantastic photo manager, one of the best!
3. 7Zip -unzip your...files! Very easy and fast!
4.VLC is a great media player but try something called GOM.
5.Yahoo Widgets for Windows and Screenlets for Linux to dress up your desktop.