Tony Byrne has an interesting article at CMS-watch: Open-Source CMS: Prohibitively Fractured?. In it he tries to come to terms with a common problem in open source development, the proliferation of projects that address the same problem but with a different programming language or design.
What appears to have happened is that development resources have become dissipated among so many different initiatives that seemingly none of them is achieving critical velocity. Moreover, an emphasis on technical elegance over end-user features goes against what the CMS marketplace is looking for today.
Another link took me to an article about Microsoft Sharepoint 2003 and hinted at what the new program will look like. My initial impression of Sharepoint has not been good. It seems like nothing more than a web browser interface to a file system used to store documents. Some of the integration planned with the next version of Office may begin to change my mind.
Both of the links above came via High Context.
Here are some clearinghouses for listing open source content management systems.