Oxfam International does a pretty good job of educating their supporters. On the bottom of its home page it has links to its rss feeds as well as to Facebook, del.ico.us, Yahoo and Google:
Next to the RSS feeds is a link to "What's RSS?" When you click on it, you see this page:
Next to the links for del.icio.us, Facebook, etc. there is a link to "What are These?" When you click on it, you see a page that explains social bookmarking:
This page could use a little more fleshing out to explain how each service works.
Another good example of a nonprofit helping folks learn how to use social web tools is the United States Holocaust Memorial Museum's explanation of how supporters can subscribe to their Voices on Genocide Prevention podcast:
Although more people have heard the words blog, podcast, Facebook, MySpace, YouTube, etc., don't assume that they actually know how to use them. Don't forget to help them out, so they can help you (: