Rails Screencast
Even if you know Rails, you should watch Ryan Bates' superb introductory Rails screencast, if only to make sure you see how to perfectly evangelize Rails to developers who don't know it.
This is a single archived entry from Stefan Tilkov’s blog. For more up-to-date content, check out my author page at INNOQ, which has more information about me and also contains a list of published talks, podcasts, and articles. Or you can check out the full archive.