I prefer Mepis Linux. Stable, based on Debian, and works across pretty much every machine I have access to. Mepis 8.0 needs only 512 Megs to run since that version is a few years old, and Mepis 11 requires only 1 Gig on more recent machines. Debian has been around for many years and is a well-established version of Linux, however a plain vanilla Debian install is not for the casual or newbie user. Mepis has some very good auto-installers built in and does a good job on detecting hardware, including video and network chips. Too, there are both 32 and 64 bit versions available for both releases.
Mepis Linux only needs 512 MB??
Well, that kind of answers a question we were discussing