For Christmas I got a wonderful present: a 1GB USB drive. Now I feel
the need to fill it with Ruby goodness, but I don't know exactely what
to put on it.

Basically I need a portable development enviroment that can be used
with OSX, Linux and Windows. Windows could be bypassed by putting a
bootable minimal live linux distribution on the drive, but then I
could find myself on a box that can't boot from a usb drive (I have
two of them at home :)).

I was thinking about:
 
Reference Documentation: Pickaxe2 PDF (that you too should buy!),
rails doumentation, who knows what else

An editor for each platform: TextMate (Mac), and don't know what to
use on win/linux

Ruby in its various forms

Everything else. Obviously I don't know or I wouldn't have asked :)

I think that 1GB should be more than enough for every ruby developer
so suggest everything you have in mind :)