If you (plan to) use the Serendipity blog software and understand German, then there is a great new resource for you. Serendipity Help is a small but hopefully fast growing collection of screencasts put together by Reinhard Linnemann. Right now, you can find tutorials on the installation process, on the first time you log in, and on Spartacus, the mighty plugin management tool. Reinhard has done a great job in creating these tutorials. Even if don't know German, you might find the screencasts useful.
If you're interested in contributing screencasts, please do so and read this forum discussion for more information. I will also try to produce some screencasts with the help of the wonderful Istanbul. Or maybe I give xvidcap or Wink a try.