With all the buzz about the free XM radio, here is a tip so you can get it for free... forever.. From a former disgruntled XM employee

Take one of your inactive radios turn it on and let it update until it becomes active and put it on a station other than channel 1.
Turn it off and unplug all wires; antenna, power, ect.
Put it on a shelf for 2 months after the subscription ends.
Plug back in after waiting
Bam, free XM radio for life
Cheers,
-Former XM employee
Done this with 3 radios before, about to do it again
How it works
Now on to some fun facts about XM radio:
1) All radios in America are RECEIVING the XM signal. There are currently no means of shooting a signal down to a specific location…and this would be even harder to track in a moving vehicle.
2) Since every XM radio is receiving the same signal they all have to be using the same encryption and decryption keys. XM has a bandwidth problem. They can’t transmit the same channel at the same time with 2 different encryption keys .
3) Your XM unit is incapable of transmitting any signal. Unless you call in and bitch they don’t know whether or not you received the proper encryption signal or not. They have no way of knowing who is listening, what they are listening to, or if the unit is even turned on.
Now, about that bandwidth problem
This is how their activation / deactivation system works.
1) An encrypted signal for your XM unit along with several others is broadcasted continually for about 2 months to activate your unit. The instant you turn your individual XM receiver on, it grabs the XM signal and is given the go ahead to receive signal, until further notice.
2) Due to the bandwidth limitations after two months of plastering all of America with you activation signal they stop sending it, thinking that in the given amount of time you have surely received the signal.
3) When your subscription runs out another signal is again plastered over America specific to your unit that says quit receiving signal until further notice, for about 2 months. After two months the deactivation signal is no longer sent out. Now this is where the magic happens. If you were to purchase a one month trail of XM then cancel and remove all power to your unit for a little over two months, allowing the deactivate signal to be sent out but never reach your unit it would never know that it shouldn’t be receiving. Then you would have free XM radio for life