Simon Guest, our resident J2EE interoperability guru, recently wrote a book detailing a number of interoperability strategies between .NET and J2EE.

He was kind enough to list me in his acknowledgements for the time spent reviewing and commenting on his work - espeically the data access stuff.

If you want to see first-hand how you can make .NET and J2EE work together within your environment, go get this book.  We've been preaching and living the interoperability story for some time now.