NetworkControl is a free (GPL) Linux (Xwindows GUI-based) utility that allows you to control and monitor your network interfaces, including wireless ones (in that case, you see a signal strength meter, as shown on this page).
NetworkControl addresses a conspicuous lack in most Linux distributions — most tend to be short on easy-to-use network utilities, even something as trivial as a robust, informative way to log on and off a dialup connection. NetworkControl also provides the connection IP, configuration and statistics (gleaned from "ifconfig" and updated each second), and provides graphic signal levels for wireless interfaces, handy for evaluating a system of wireless devices.
NetworkControl allows you to see network activity at a glance and lets you control your network interfaces in a fast, convenient way. It is designed to be informative and easy to use.