XBee configurator for OSX, linux (and windows)
xBee modules are nice, but configuring them manually with AT commands can be quite frustrating (but a great learning experience). Digi, maker of XBee modules, offers the X-CTU application to easily configure the modules, get/set the various parameters and more. Unfortunately this application is Windows only. Now there is a cross-platform alternative from moltosenso, an italian company providing a free GUI application to configure and talk to the modules over serial.
Try it out: moltosenso Network Manager