Umbraco is a free, open source CMS written for ASP.NET. I looked at it a while ago, but for a couple of reasons I stopped working with it. Now, they’re at release candidate stage for version 4 and it has a bunch of new features including finally switching from their proprietary membership system to supporting the ASP.NET membership and role providers.
I might give it another look to see if it’s worth using. What was very cool about it from the standpoint of developing a web site, was that it provided all of the functionality for data storage and content management, and as the web site developer you only needed to really focus on the UI aspects of the site. One of the downsides, in my opinion, was that all of the content remained in memory in XML storage, which means that as you get more content your memory usage is going to increase. I was concerned about this at a shared hosting level, but then again, I guess it would require a lot of content before that became a problem.
I’ll probably start playing with it again and seeing what I can do with it, and will blog about the results for anyone else that’s interested.