I too hate treadmills and lifting weights -- it's just dreadfully boring. However, if you pick up a sport, you can hone your coordination skills and progress to become a better player. I find that it's much more motivating when you're competing with people. And, I feel much better knowing that I am acquiring a useful skill that can be measured against in competition.
Personally, I play competitive table tennis (very unlike garage ping pong). What's good is that you can actually do this inside, and, it's cheap to play at clubs. It's also a sport that keeps your mind sharp. I even wrote a whole article about why I think it's a great hacker sport: http://jamesyu.org/2009/01/11/why-table-tennis-is-a-great-ha...