Ajax.NET Professional - join
With Ajax.NET Professional you are able to build AJAX Web Applications the fast way, more details: http://www.ajaxpro.info/ AJAX implementation for .NET Micro Framework comming soon: http://netmicroframework.blogspot.com/
Low activity, 6004 members, moderated, restricted

Jayrock - join
Discussion group for the Jayrock project (JSON and JSON-RPC for Microsoft .NET).
Low activity, 231 members, restricted

microsoft.public.dotnet.framework.aspnet - join
Microsoft .NET technology newsgroup.
Low activity, 7026 subscribers, Usenet