John, Tupac and Kieth enjoying a long day in the Canyon
Build yourself some parallettes like these:

Go here for instructions on how to put together this simple DIY project. It is very inexpensive as well!
Why do you need these you ask? Well, parallettes are a great training tool for core and upper body strength. L-sits, push ups, tuck planche, hand stands, hand stand push ups to name just a few of the basic exercises you can train on parallettes. Furthermore, you can take them with you where ever you go.
check out the American gymnast site for detail description of these great exercises http://www.amgym.com/home/index.cfm
Happy training
Rayne