Here is an example of what I call a movable chord shape, take a look and see what you think:
http://www.dolphinstreet.com/guitar_lessons/chords
Some of you already know this, but for some maybe it can open up some ideas.
Songs I play that uses these chords: Let it rain/Amanda Marshall, All along the watchtower/Hendrix, Heads Carolina/Joe Dee Messina, etc...