everyone interested in bodyweight workouts should seriously check out local playgrounds and parks. it may sound odd, but in denton there is this awesome park with all kinds of crazy equipment that can be used for making calisthenics more challenging. examples: the rings (all kinds of pullup variations that are impossible with a bar), parallel ropes (good for making pushups and dips involve stabalizing muscles) etc, etc. if you are creative you can turn a playground into a freakin gym (and its free too).
The kids look at you weird, though.
It's already been marketed!
If you grip a small child by the leg, it's superior to a kettlebell for ballistic movements.
lol @ SDriver!
I watched the Thug Workout.....its´totally crazy but cool and they have some unique exercises there.