I found a few good links from the blogosphere today:

A .NET RSS implementation. It may conform to the spec, but I don’t think it’s created to handle reading other people’s crappy (read: incorrect) RSS feeds well.
Partake in a WPF contest – Might be a good way to dive in and start learning the technology.
Jack Gudenkauf posts about Add-In model(s).
Taking advantage of Vista in your application – on Codeproject