My current favorite indoor bike is the Keiser M3. It works without the 38 - 42lb. flywheel pulling your legs around, instead using magnetic resistance so you have to supply the power. Also, you can get it with a computer so you'll know your power output.
I've been teaching this format for over a decade and this is the most excited I've gotten over a bike that doesn't actually go anywhere.
Check out their site:
http://www.keiser.com/m3/index.html