You can sign up for 1 year contracts on most carriers.
__________________ The difference between stupidity and genius is that genius has its limits. When you take things for granted, the things you are granted, get taken. Even a mosquito doesn't get a pat on the back until it starts to work. Too many people miss the silver lining because they're expecting gold. [BES 5.0.3 / GroupWise 2012 HP2]
Actually, I think they just about all "require" a 2 year contract. But, it's meaningless if you bring your own phone. The only penalty associated with those contracts is an Early Termination Fee (usually $175), but they can only charge you that if you got a phone at a promotional price when you signed the contract. Otherwise, you have a "contract", but you can cancel it any time with no penalty.
My $0.02. But, I'm no lawyer...
Verizon 8130 (on the bench, now
Verizon 9530 (replaced by VZW 4 times, then with a 9550)
As far as I have seen ALL the carriers offer a month to month contract, you simply have to go into a store with your device and activate service. With a BB you will still have to add the data plan but you are not locked into a long contract.