The new MSDN Forums
If you haven't already, be sure to check out the new MSDN forums site that just went up recently. It's got a ton of different message boards and there's already plenty of activity going on.
If you want to jump straight into the C# related forums, head over here.
Also note that each forum even has an RSS feed you can subscribe to to stay up to date. For example, here's the C# language feed.