I completly agree with using cmsmatrix in order to determine which CMS suits your requirements. It's my first place of call when ever I am faced with that decision and I have found that site very helpful through out the years.
I recommend only three: Joomla, Wordpress and Drupal. From this list, take your pick based on your needs or requirements.
wordpres jhoomla drupla and so many more. best is to try out each but finally its the human that matters.
If you need simple CMS which will be easy for your clients to manage I suggest CMS Made Simple or ImpressCMS. CMS Made Simple is really plain and simple, ImpressCMS is also simple plus it won Most Promising CMS Award 2009 by PacktPublishing. Also, check this in depth post about choosing CMS, I believe it can be of great help.