If you're considering a CMS for a Web site, you might want to have a look at http://www.opensourcecms.com .
From the site:
CMS/portal systems featured include:This site was created with one goal in mind. To give you the opportunity to "try out" some of the best php/mysql based free and open source software systems in the world. You are welcome to be the administrator of any site here, allowing you to decide which system best suits your needs.
The administrator username and password is given for every system and each system is refreshed on the hour, every hour. This allows you to to add and delete content, change the way things look, basically be the admin of any system here with no fear of messing anything up
There's also full admin demos of free open source blogs, forums, groupware and e-learning programs. All programs are PHP baseed, and most use MySQL back ends.