Remember those 10,000 Fon routers that were given away? They should be arriving at your home soon (at least mine did, today) and what better to do than crack her open and start modding away.
Out of the box the foneros wireless router has Telnet and SSH turned off. By accessing the buit in serial console you can turn SSH on and access various settings and reflash the firmware.
You will have to bust out the Dremel and get your hands dirty for this one, but at least it allows you to turn your already free router into a better free router. Hit the link below for detailed modding instructions.
Oh, and Comcast users: if you ordered your free Fon router, using it actually violates your EULA so you should mod the hell out of it anyway, or at least give it to a non-Comcast user to further expand the Fon network.
Accessing serial console on the Fon [DD-WRT]