Reddit mentions of Essential Rings 2.0 - Gymnastic Fitness Great for Crossfit Exercise Training Gym Pull Ups

I dont know what kind of rules exist regarding hanging from trees, but buying (or making, somone had a link to a howto around here in the last day or so) a set of Gymnastic Rings might provide a light piece of equipment to carry in but allow you to do all kinds of stuff.

Once I am in better shape to use them (Im not strong enough currently) I think I will add them to my routine as the workouts look pretty awesome.

I know it's not what you've got listed as something you really want, but:
http://www.amazon.com/GoFit-GF-PUB-Push-Up-Bars/dp/B0007W2FLS/ref=sr_1_3?s=sporting-goods&ie=UTF8&qid=1320159827&sr=1-3

These are really good. Coach Sommer, author of the book which I also read and love, really recommends doing a lot of l-sit work. If you can get to the point where you can hold an l-sit for even a couple seconds, those pushup bars are your best friend. Seriously, wake up and hold an l-sit on those suckers for a few reps, and your abs will be tough as nails quite quickly.

As far as rings go, don't go cheap. If you want to make your own, make sure you find a guide that will build rings to support your weight. I bought:
http://www.amazon.com/Essential-Rings-2-0-Gymnastic-Crossfit/dp/B0030CEHYU/ref=sr_1_1?ie=UTF8&qid=1320160318&sr=8-1


They have treated me extremely well, and I have made a lot of progress on these rings, from barely holding myself up to doing a muscle up to planche to handstand on them. They are still good as new. They are like 37 bucks and are available with prime, so it's a pretty good deal. If you're willing to spend some more money you could actually get a nice pair of wooden rings. They are pretty nice and work well with chalk.