Not really a programming question but it was the most suitable to post in.

Does anyone know of a CMS coded in .NET (preferably open source) that works in a similar way to Mambo/Xoops?

I'm sure there are a few out there. Rainbow (http://www.rainbowportal.net) is one that is Open Source, written in C#. Most ASP.NET scripts I've run into are for-pay deals. I suppose it stands to reason that developers of open source apps are more likely to develop on open source platforms.

Found a really good one - has a huge following aswell which is always a good thing with open source.

http://www.dotnetnuke.com/