Contained here are several sample Jam setups. Each has a README.html explaining the specific example. You can use this set of examples as a sort of Jam tutorial, or as a starting point for your own projects.
simple - Hello world revisited
abstract - Abstract multi-directory project
rootless - Project with multiple independant sub projects.
These are listed in order of increasing complexity, so if you're looking at Jam for the first time, try going through the examples in this order.
Happy Jamming!