CMS

I'm researching a suitable CMS for a website ran by a group of vollenteers. So it needs to be simple to maintain and update as well as stable and professional looking.

Edit: forgot to mention it's most probably a very low page count website at this point.

I have a few in mind but thought I'd open it up to the community to see if you guys can throw in any new ideas, so what is your favorite suitabe CMS and why?