MacStumbler is a small utility I wrote to emulate the functionality of projects like netstumbler, bsd-airtools, and kismet. It's meant purely for educational or auditing purposes, although many people enjoy using these types of programs to check out how many networks are in their area, usually known as war driving.
Most of the features of MacStumbler can be summed up in this screenshot:
Download MacStumbler 0.5b. (warning: still beta! please send me bug reports) You might want to view the changelog or todo list.
Hardware/Technical
MacStumbler only works with airport wireless cards, it does not (yet) work with any other PCMCIA or USB wireless devices. Apple didn't provide any information on interfacing with their airport card driver, so I had to reverse engineer the functions required to actually preform the scans. I'm not quite ready to release the source completely, but if you're looking for information about how to do the same you can download my Apple80211.h.
To enhance the scanning results, many wardrivers like to use external antennas to increase the range. The new ibooks and tibooks both contain an antenna built into the screen which can provide much better range than standard pcmcia cards by themselves. This antenna is directional, I find my ibook gets the best signal when the screen is facing away from the access point.
Bugs