PortableApps Suite 1.0
via lifehacker:
Windows only: PortableApps Suite 1.0 stocks your USB drive, portable hard drive, or any other drive with a full complement of software, ready to run wherever you plug in.
This new version of the suite includes the latest portable versions of Firefox, GAIM, OpenOffice, and other open-source gems. The suite also comes with PortableApps Backup for–you guessed it–making backups.
If you have a 256MB of bigger thumbdrive colleting dust, this is definitely worth checking out. Revew the full suite at portableapps.com.