Depending on your budget there are a few good trainers. The three best are the Kurt Kinetic Road Machine; the CycleOps Fluid 2, the Magneto if you want to save a little money or the Mag if you want to save even more; and the 1UP CPR A2000.
You won't go wrong with any of them. The cheaper Magneto and the Mag you could outgrow, so if you plan on training hard and want a trainer that will keep pace with your growth then get the better Fluid 2, Kurt Kinetic, or 1Up; like I said earlier, I think the 1Up is the best one on the market. You can get more expensive trainers with computers and sorts of fun stuff which I've never had the need for the frills, but if want a good basic trainer those are the ones.