Usually, you can buy a device outright without getting into a contract. Of course the price will be closer to the manufacturers suggested retail price.
Of course the downside, is that in the US, carrier branded devices will only work on the carriers network. ex, if you buy a phone from AT%T, it will only work on their network. It's what we call a "locked" phone.
If you were to "unlock" the phone, which is legal to do, and use another carriers network. At best, you would be limited to 3g.
Whatever you do, I suggest a GSM (sim card) phone, as if you travel a lot, you can get local sim cards thus saving you a lot of roaming charges, especially when abroad. Of course you'll need to get the "unlock" code to do this. I've heard reports sometimes the people where you buy this device, will sometimes be nice and do this for you.