Tinycore is a possibility, but you have to be careful about what you install and how you install it. It runs from RAM, you start with just 10mb or so, which is the basic running system, the "core". You have a GUI, a file manager and an App Browser along with a couple configuration programs. Everything you want to install is known as an extension. Extensions are loaded into ram before they are run, so they end up taking more space than they might in a conventional distribution. You have to think about dependencies too, in the App Browser's size tab it will tell you what everything will take.
Depending on what you want out of the system, it is very doable. Forget Firefox(23mb) or Chromium(32mb), go with Dillo(2mb) for a browser. Something like XMMS2 to handle music because it is only 8mb. Mplayer for videos is going to be about 12mb, where as VLC would be nearly 40mb. You're not going to have OpenOffice, but Abiword will handle most word processing tasks and is only 20mb.
That isn't to say once you fill your RAM it will stop working, but it will start going into swap, which will kill the responsiveness of the system.
It is a very interesting distribution, I just started playing with it recently on an early EeePC with 512mb of RAM.
Last edited by elliott678; 03-19-2011 at 02:50 PM.