Ideally I would like to marry .Net and Java with JMS as I am not a big fan of Web Services. Compared to JMS I find Web Services to be verbose and complex.
What is required is a Windows Communication Foundation binding that can be used from Silverlight 2, .Net 3.0/3.5 and .Net Compact Edition (Windows Mobile, PDAs, etc).
I saw a .Net API slated for development in Version 2 but I have yet to see any details. It would be nice if this API was accessable from WCF via a binding.
There is a FAQ for that.
You should try Stomp.
We have an opened task for JBM 2 / C++ and .NET integration. We are working on other fronts before we get there.