have to agree with buzzbomb on the 1upusa trainer. I looked at several. Talked to several shops about fluid trainers and found them to have a few problems i didnt want to deal with. I have been very pleased with the 1up trainer. You can run a variety of wheel sizes and you can set it low enough to the ground that you dont need a front wheel block to level the bike. Its relatively quiet and smooth. If you want a little more input, go to mtbreview.com and look at what people have to say about other trainers. That was where i found the 1up and have had no regrets. you can also pickup a computer to go with it if you wish to track cadence, speed, distance and such for your training. The magnet to read wheel speed is built right into the roller and they had already calibrated the computer for me when it arrived. I have had no problem with mine, but for those who have, said customer service has been great.
If you do get one, consider buying a second wheel for the rear. A cheap one will do as your not going to be abusing it like you would with your current wheels. A simple deore hub and inexpensive wheel would work great. Also a smooth tire to help reduce noise would be a good idea. I run a specialized nimbus on mine and its pretty quiet.
Good luck in your search.