perhaps one of the success stories of foss and in the sold arena to. Most of the mainstream vendors do a variation on the cms which they charge for and umpteen startups and other vendors do cms’s which are either free to use and or both free to use and you can obtain and hack the source as well.
cms is a real catch-all acronym and the functionality of them varies wildly, some being little more than blogs, or bulletin boards to the ones that manage content in quite sophisticated ways with versioning etc and even the ecms, enterprise cms that will manage you web across multiple sites.
cms watch lists, looks at an analyses cms and they break them into 4 groupings. ‘Web Content Management Vendors’, ‘Enterprise Content Management Vendors’, ‘Enterprise Search Vendors’ and ‘Enterprise Portal Vendors’