One of my hobbies is art. Really has no prep value, but we like making our home an interesting place...or Nerdvana as some of our friends have called it. We do a lot of muraling, and most in the family are artists, so some of our own framed art up as well.
Another hobby is we enjoy meeting celebrities who are in shows we like, at conventions. I've had a drink at the bar with Sir Anthony Daniels (C-3PO), cracked jokes with the actors who played Warf (on STNG), and "Ello Bobbit" pirate (from Pirates of the Caribbean), and talked about horses with Wilma Deering (from Buck Rogers). It's really pretty fun, and a lot easier than folks think, to catch these folks at good times when they aren't signing autographs, etc. So far, most really seem to enjoy being treated just like normal people, and just shooting the breeze at times.
Costuming/cosplay is another. We have a closet and bins full of costumes and accessories for different characters and costumes. Typically, when we go to a convention, each of us has about 6 different costumes we could alternate into (so a different one each day, or more).
Most other hobbies are prep-related in some way. May not have always been the original intention, but they do seem to relate, so... Even paintball (another fun hobby), is pretty much prep for firearm combat and tactics.
