Windows Workflow Foundation
If you are in the planning stages for a new .NET project I strongly suggest taking a look at Windows Workflow Foundation. Of course it isn't released quite yet but it's in beta 2 so anything out there isn't going to change a whole lot.
So why is Windows Workflow Foundation so interesting? Well most applications I work on, and I suspect the same is true for pretty much every other database application, contains workflows. Sometimes these workflows are only implemented through work practices and not really enforced in code. Most of the time however these workflows are implemented in the application code, so far nothing special. Now Windows Workflow Foundation changes things a bit. Previously both the workflow and the implementation of rules and activities would be developed in the same language making it hard to distinguish the flow from the implementation. Not anymore :-) The Windows Workflow Foundation designer gives a clear overview of the workflow without bothering you with the implementation details. On the same accord, you can now look at the implementation of a single action without being swamped by the complete workflow implementation.
And best of all, the workflow can be updated at runtime allowing for far greater flexibility. In fact you can even include the designer in your application.
To get started go to http://wf.netfx3.com
where you can find the download for Release Candidate 2 as well as a load of samples and documentation.