Before I continue pointing out SDK samples, why not take a look at a great end-to-end .NET Framework 3.0 demo first? It's been out there for a while and hence this isn't really news, but in case you've not seen it (or the latest revision of it) go check out DinnerNow. The demo covers WCF, Workflow, CardSpace and PowerShell. Awesome piece of work from our Evangelism team.