Windows Phone Thoughts: Rent Your Phone From Rentoble

Rentoble will allow you to rent the latest phone from the four major US carriers, or rent an unlocked GSM phone to use wherever you want. When you are done, just send the phone back and pick out a new device. They don't have every phone the carriers handle. For example, for T-Mobile they only have the G1 and Sidekick LX, and for AT&T a couple of Blackberry's and the Samsung Epix. The only Windows Mobile devices I saw were on the Sprint and Verizon networks.

If you are the kind of person that is constantly buying a phone, then selling it after several months when something new catches your eye, this might be a cheaper alternative.