I have seen this used in the verses of Johnny B Goode and Think about You (Chuck Berry and Guns n Roses). They use a regular power chord shape but about every third 'strum' (if that makes sense), they change the chord so that the second note of the power chord is moved up one step by using their pinky to play it. I was just wondering if this has a name or is a certain technique. Here are the best examples:
http://www.youtube.com/watch?v=OrOQQHQnxlo&feature=related He does it at 18 seconds and on


http://www.youtube.com/watch?v=XKzuI52V7iE He does it at 22 seconds and on.

This is a common blues guitar rhythm. I think it's most commonly used in 12-Bar Blues, so have a look at some 12-Bar.