Treadmills aren't the best place to train, but sometimes they're unavoidable, especially in the winter. Here are three of the best at three different price points.
Start out with the 5.0, and if you are serious, consider getting something top of the line. The more you like it, the more you'll actually use it!
You also may want to read a thing or two about buying a treadmill.
(If you're on a budget, look for treadmills on eBay.)