I used crucial pc133 ram in my last machine and was quite happy with them. Very good deal when buying from their web site. When I upgraded to DDR, i wanted a good brand a little cheaper as well. I ended up buying OCZ Technology PC2400 DDR CAS2. At the time I was able to get a 256MB stick for $49.99, which was cheaper than crucials PC2100 CAS2.5 at the time. I have been quite happy with it, and other's have said good things about OCZ.
I bought mine from...http://www.hardcorecooling.com
I think the prices have went up since then though, just like all other sites.
If you buy a pre-packaged pc, shame on you :wink: