Check out Kismet. In particular the IDS (Intrusion Detection System) features. The docco can be found using Google.
Theres a tool listing on the BackTrack wiki which you can use to find out whats available for you in BT, and there are obviously a bunch of HowTos and Videos on how to do various stuff right here on this forum. Its just a matter of what you are interested in really - you can try almost anything relating to pentesting and also to a variety of other IT Security related fields. You might want to have a look around the various tutorials on the forum and see what interests you. If you can be more specific about other things you are interested in, we may be able to point you to some specific resources.



