mamboo and joomla are two good ones, however these have become very huge, and what I belive most of the people will find it difficult use when customizing different parts.

I am currently developing a new CMS, which will be FREE and OPENSOURCE, and it will be extrmely easy to use for full management of your website, I have already designed a couple of very eye cathing designs for it. I will probably post it here for you to download, it may take a few more days..

but for now if you like you can use joomla or mamboo..

cheers