There is also an NGP Tutorial that can be used to learn about NGP. It includes suggestions on how to move from NGP to real AWT and Swing.
Currently I (Matt Chotin) am the maintainer, so you should mail me if you notice any bugs or have any comments. However, if you're in CS15, be very sure that you have an NGP bug and not with your program. I have written all of the programs using NGP, and they all work fine :-)
The documentation should link correctly to the standard Java API, but for your convenience, it's also linked here. The three relevant files that we use a lot are: