It all depends on what you want it to do. Must Linux distros will come with a basic installation that usually takes around 500MB of disk space. If you don't want a GUI with all of the extra apps then you can shrink that to about a quarter of that space.
Red Hat/Fedora is very user friendly, and with everything installed (including dev tools) the total space will be around 1.5GB. As for memory, 128 is fine and you shouldn't need any more then that.
http://www.linuxiso.org/ <--- is your friend. Check the forums and get the links/guides there.
Red Hat 9 with a nice KDE gui is usually what I recommend. Other distros would be Mandrake, Debian, and SuSE. Look into those, nice features and support.