Often when I'm at a client's site and need a good, flexible linux toolkit, I use Linux Mint (11 currently) on a usb stick with a 4GB persistent file.
Mostly, the PC's I work on at Client sites have > 512MB. Occasionally I do encounter a PC with less memory and even though I use LXDE (lightweight desktop environment) I run out of memory pretty rapidly. (Web Browsers especially...)
A quick run of "free" shows 0 swap and confirms why applications are silently vanishing:
total used free shared buffers cached