http://www.portablefreeware.com and http://www.portableapps.com are two good site for free portable software.

Are you using any portable software, and what software are you using if you do?

I really like the PortableApps suite. It has actually drawn my attention to other cool open source programs that I have installed in the non-portable form. That's how I discovered ClamWin and PDFTK.

Two quick Windows apps I like that run portable:

1. Snippy, a little screen capture program. I love it for blogging.
2. uTorrent. This can be handy if you want to download and install a open source program at a friend's house. I've done this before when I installed OpenOffice and saved the day.