PortableApps.com = ultimate win
At least if you use multiple computers. PortableApps.com is a free and open source software suite that contains a bunch of useful programs that execute from your flash drive and leaves nothing on the host computer when you’re done. It includes a browser, calendar and contact client, mail client, antivirus software, openoffice, and bunch of other cool stuff. There’s also like 11ty other programs you can add. The main suite is around 90Mb.
My 8GB thumb drive now sports Firefox with add-on’s for an FTP client, adblock, and gmail notifier, a full office suite, a picture editor, pidgen IM, a full financial suite, a backup utility, an antivirus that’s capable of checking both the drive and the host computer, an html/code-centric text editor, a compression/extration util, and a media player, all executable from the thumbdrive ftmfw.
/nerd
Oh yeah, and there’s over 7GB left over for storage 
