Beyond the MENSA appraoch, I'd look at your cluster of interests and match that to groups with similar interests. One that may be a great match is to find a local Hackerspace. Typically these are a group of people at core passionate about learning new skills and knowledge sharing.
http://hackerspaces.org/wiki/If you have an interest in science fiction, you may find a lot of like (and generally smart) minds at science fiction conventions.
Or take adult learning classes in subjects of interest at a college and see about hanging out with folks afterwards.
Ultimately matching passions seems stronger than matching aptitudes. If you are in a larger city, MENSA may do both as they have SIGs (special interest groups.)
