I just have to mention one of my new favorites. The website www.portableapps.com has a great program suite for portable applications. Their suite works with most portable hardware (USB flash drive, iPod, portable hard drive, etc.) and for those that do not wish to use the entire suite they also have a pretty nice library of portable applications. Best of all – its completely free.
I personally use their Lite Suite. OpenOffice was a bit much for me to put on a thumbdrive and between the Lite’s AbiWord and the fact that most pc’s have office software I decided against it.. I’ve customized it a bit so with the suite I always have Firefox, Filezilla, Notepad++, Foxit Reader, and 7-Zip just a few clicks away on any computer.