Kismet is a 802.11b wireless network sniffer – it is different from a normal network sniffer (such as Ethereal or tcpdump) because it separates and identifies different wireless networks in the area. Kismet works with any wireless card which is capable of reporting raw packets (rfmon support), which include any prism2 based card (Linksys, D-Link, Rangelan, etc), Cisco Aironet cards, and Orinoco based cards. Kismet also supports the WSP100 remote sensor by Network Chemistry.
Utilities such as this will become more important as 802.11 networks overlap, mesh, and do other stuff that we haven’t thought of yet. There’s also another reason to covet a Sharp Zarus.