I'll add an obligatory plug for F# if you're looking for a fully supported .NET language REPL (as opposed to a side project like scriptcs, not that there's anyt

I'll add an obligatory plug for F# if you're looking for a fully supported .NET language REPL (as opposed to a side project like scriptcs, not that there's anything wrong with it). As a bonus, F# is now fully supported by Xamarin Studio if you want to use it on non-Windows platforms, which means that in addition to a REPL, you have full IDE support for free on each platform.