Sarah Ludwig blogged about how to learn Scratch over on the YALSA blog. She gave a nice shout out to Media Mashup:
Media Mashup. This site, created especially for libraries, offers a lot of cool stuff, including its screencasts page. The pirate ship tutorial was the single-most-useful thing I did in preparing to teach Scratch. I probably said “ohhhhh, OKAY,” about a dozen times while watching it. It introduces you to the “puzzle piece” or “building block” concepts that make up Scratch, and shows you how the commands that you give objects make the objects do stuff. I recommend just jumping in and doing the pirate ship tutorial even if you have literally never used Scratch once.
She also documented other great resources and her process in learning Scratch as an educator. You can read the whole story on their blog here: http://yalsa.ala.org/blog/2011/09/16/30-days-of-how-to-16-how-to-us...