What about the idea of riding fixed-gear to supposedly help out your ability to spin at high cadences? It definitely forces you to spin and work on not bouncing, but the bike is doing the work, rather than you (assuming you're going downhill).
I'm still unsure how I feel about riding fixed helping with my regular cycling. I try and get a 40mile ride in once a week on the fixed gear that includes some hills that I can hit 40mph easily on a regular road bike. Obviously I have to hit the brake before getting anywhere close to that speed, but I do try and spin like a madman as long as I can. However, I feel like riding a fixed gear works against you. I feel as if my legs get lazy and become accustomed to the pedals pushing your legs. Once I hop back onto a regular road bike, more often than not I almost feel slower and less efficient.
Anyone have any thoughts on this?