There are some great instructional videos available for free on YouTube. Sometimes it's difficult to separate good information from bad. As with the Mandolin Academy page, my goal is to, over time, add to this page some of the great instructional material freely available on YouTube.
Brad Davis is about as good a player and teacher as you can get. This is a fair and thorough explanation of the pro's and con's of different right hand techniques. It's very matter-of-fact, and instead of saying that there is only one way to play, gives several reasonable possibilities. I think this is important, as every person's body is different, there is no one technique that will work for all players.