What, with Microsoft releasing new stuff, but Portable Suite 1.0 kicks arse. These apps are arranged to run from a portable device, such as a USB stick, and there's a nifty menu included. Theft of description is from the site:

PortableApps Suite (Standard Edition): ClamWin Portable (antivirus), Firefox Portable (web browser), Gaim Portable (instant messaging), OpenOffice.org Portable (office suite), Sudoku Portable (puzzle game), Sunbird Portable (calendar/task manager) and Thunderbird Portable (email client) and runs comfortably from a 512MB drive.

PortableApps Suite (Lite Edition): Uses AbiWord Portable (word processor) instead of OpenOffice.org Portable and runs comfortably from a 256MB drive.

PortableApps Suite (Base Edition): If you'd like to pick and choose exactly which apps to include, you can try Portable Apps Suite (Base Edition). This is a stripped down package with just the PortableApps Menu, PortableApps Backup utility and custom folders, icons and autorun. It's less than 1MB installed, so it's a great option for smaller drives.