WiFind – Wireless Network Locator.
WiFind shows you if wireless networks are locked or unlocked and their signal strength. It is a tiny lightweight plugin for OS X that makes connecting to reliable wireless networks quicker and easier. Whether you are at home, the office or at your favorite cafe – WiFind will help you locate a signal and start browsing!
Demo for Mac OS 10.4 (Tiger) and 10.5 (Leopard)