People interested in Mono and the CLR should take a look at OpenLink Software's Virtuoso product. It enables you to run .NET code on both Windows and non-Windows platforms through its Mono implementation and also supports Web services, including standards like WS-Security and WS-Routing.

One of the most interesting product features is its support for CLI compliant code exposed as stored procedures, triggers, and used as custom types in the Virtuoso SQL engine. This is similar to the functionality people are waiting for from Yukon. More information is available here.