interval training and endurance workouts on machines. i know it's lame but if you stay on a stationary bike and just work REALLY HARD twice a week it's better than having to deal with real world riding.
then again, if you know how to train you can do it on the road pretty successfully.
the only thing you need to buy to gain speed is food, and sometimes expertise. you don't need power meters and you don't need drugs/coaching/ultralight racing components. you just need your bike and your muscles and your brain to tell them what to do. strength is about your brain being able to work your muscles to exhaustion and your digestive system being able to build them up stronger.