First, the news server is msnews.microsoft.com
If you search for any newsgroups on that server for 'dotnet', 'csharp', etc. you're bound to find several.
I personally use the csharp, windowsforms, windowsformscontrols, and adonet groups. They have several others for webservices, remoting, etc. I wish I could read more, but there are only so many hours in a day! I believe several MVPs and MS people monitor the groups.
Kevin