Cable locks and U locks are great but are a bit troublesome to use. It always takes me a minute to wrap my cable lock around my bike frame. Wouldn't it be great to have a system that was lock-n-go?
Apparently you can get what's called a "ring lock" for your bicycle. It securely bolts on to the frame, and all you have to do to lock your bike is turn the key! It does this by locking through your spokes. No fiddling around. I imagine this would be great if you live in a low-crime area or if you just want to park your bike and run into a store(and not have some junior high school student ride away with it). Still keep a cable or U lock for longer term parking, but I like the added peace of mind!
Velo ORANGE sells their own bicycle ring locks for $25 each!