That would certainly be an interesting project, especially if you did it in such a manner as to really take advantage of the .NET platform, C# 3.0 language and LINQ rather than doing a straight port. I imagine the active record part would be the most involved.
It is an interesting idea. I've went over to the codeplex site to check out their mvc web framework. They have several projects addressing mvc but it doesn't look like anyone has tackled adding linq yet.