If you just want a fairly basic website... article content with (or without) user comments... http://www.cmsmadesimple.org is rather nice in my opinion. There are some "advanced" modules, but most of them (last I checked) were fairly underdeveloped.

Otherwise, I agree with SwellJoe. The effort required to force the CMS into doing what you want it to do can grow hideous. I built an online community site a couple years ago, and was a much happier camper writing only the code I needed myself.