I am putting here links to some old posts (not mine). The context is relevant right now because of the VS 2008 and WPF 3.5 launch.
Okay, so this is not something new. People have been talking about these features since many months now. But for some (including even me, because even I am not yet familiar with all of the new features), this may still be a novelty.
Check out this article by one Daniel Moth