Some people say "Don't skimp on ram" since it can cause problems. My experience with no-name generic pc100 has been quite good, however. A friend of mine runs all his boxes, even servers with generic and has not had any hiccups (although they do run unix
Anyways, don't spend a god aweful amount on ram. Usually generic should be fine, but look around for name-brand stuff like Lanik mentioned. If they're not all that much more, it'll be worth the extra cash if not for anything other than peace of mind.
btw - Ahz is selling a few dimms. I got dibs on the 128mb stick he's selling, but I believe he's got a 256mb stick too.