Global Jam is a unique time for folks to get together across the world and celebrate ubuntu. As part of the celebrations, there is an opportunity to download the latest beta (released yesterday!) and check out the next version of ubuntu. You can run it in a livecd or perhaps in a virtual machine. Ether way, there's opportunities for you to test the common applications and report your results.
The testcases are available here: Ubuntu Global Jam Testcases. For some of you, this page may seem a bit funny, but fortunately there is a handy walk-through for you to understand how to use the tracker and specifically, how to report results against these tests. Check out the guides below. If you follow the link, you'll even find some video of yours truly giving you a visual demonstration.
If you get stuck, remember your friends in #ubuntu-testing on freenode are also happy to help. Have fun jamming, and if you do test, Happy Testing! Most of all, celebrate ubuntu!