There are quite a few resources out there to help with learning the Toolkit. Whether you're a new user or a Toolkit Pro, there's something to learn for everyone here. If I've missed anything, let me know:
UPDATE: Coding Atlas is another great blog. The other takes the time to convert their experiences into walk throughs that are really cool. Check it out!
UPDATE: AspAlliance also has a set of really cool videos on the Toolkit as well: http://aspalliance.com/videos/