OK, so you've got all the bits downloaded and installed on your machine. What's the best way to start to get familiar with everything we've added to Silverlight 2?
Well, you could do worse than start with the thirty page hands-on lab that I spent part of last week frantically working on! This lab takes you through the various steps of creating and packaging an application, figuring out layout and controls, all the way through to creating a mini-game using Silverlight 2. It's a good lab to get familiar with XAML, Expression and the new Visual Studio tools.
Once you're done with that lab, there are a number of others that you can go through to add depth to your knowledge, written by Adam and Laurence. Download them here. And if even that isn't enough for you, there are some tutorials here that Jesse Liberty has been working on. Hopefully that's plenty to get you up and running for now!