Is MEF Silverlight only, or can it be used with WPF apps, too?
MEF is definately available in WPF. That I know of there are currently 3 versions of MEF, of which 2, the version available at http://mef.codeplex.com and the version baked into .NET 4 are both usable, and indeed beautifully compliment, WPF.
MikeC/Tom,
MEF is coming with .NET Framework V4 and Visual Studio 2010. It's there in the RC right now.
It's also coming with Silverlight 4. It's there in the beta right now.
There are also source-code versions of MEF on CodePlex. One is for Silverlight 3 and the other for .NET Framework V3.5 Service Pack 1.
Hope that helps and, yes, that means it's great for WPF applications as much as Silverlight applications plus you might even get to share some source code between the two.
Thanks,
Mike.