Test your network configuration and detect rogue access points.
Setting up a wireless network isn't easy--and the hardest part is making sure that you have it working properly. Netstumbler helps you optimize your wireless network by showing you whether it has any holes. With NetStumbler, you can locate WLAN areas with poor coverage and detect other networks that may be interfering with your network. You can also detect unauthorized access points.
NetStumbler is donateware; that means you can use the software for free, but you can show your appreciation and support future versions by donating at the software author's site. The author refers to it tongue-in-cheek as "beggarware."