Portable Python
Portable Python allows you to run Python “directly from a portable device, enabling you to have, at any time, portable programming environment.” It’s a single zip file and is based on Python 2.5.
And the cool part is that it includes Django!
Update: So I loaded Portable Python 1.0 to try it out, and so far I’m very impressed. It was a snap to install (just unzip) and it comes with a “script runner” that makes testing applications easy:

I think this has just earned a spot on my portable drives. :)