I've found a sport I've never heard of before that I really want to get into this summer if I can afford one: Mountain boarding!
They are controlled similarly to a snowboard but with wheels, and can be used at ski areas during the summer. They even have bindings with ratchets.
This is a Trampa mountain board:
To me, this is easily the closest thing I could do to snowboarding during the off-season. I really want to try it.