One thing about limited equipment at home, there are a few exercises that are hard to do. We makeshift all the time, but I recently came across a simple tool that provides a lot of options for bodyweight exercises: a pair of mobile but stable dipping bars called the Lebert Equalizer.
Here's a quick video of Mark, the designer, running through a variety of exercise possibilities; here's the same guy doing some playful and extremely difficult over and unders.
You'll find a listing of some of the exercises you can do with the Equalizers here,, and this pdf combines the suggestions and photos into a simple, printable format.
At $99 ($117 including freight) for a pair of bars that you can do a whole slew of exercises with, that price is not too bad. Some of you can make your own, I'm sure, but when you get done, will they work that well and be a lot cheaper? I'm not so sure.