Originally Posted by 12strings

Definitly interval work. If you're looking for something that will help you on a velodrome, short high intensity intervals are what you want. I've done the following for the first time over this past winter, and noticed considerable gains:

-4 minute warm-up.
-30-seconds all out, followed by 30-seconds of easy spinning (Do 5x, then spin easy for 5 minutes...repeat 5 more if you're up for it).
-3 minute cool-down.
(I do a 20-minute ride like this and I'm toast.

Sometimes I alternate those 30-second intervals to focus on different things, and to give different body systems a break, so it ends up like this:
1st = faster spinning easier gear, but all-out hard and fast
2nd = really slow hard gear, still going all-out, but building muscle strength
3rd = faster spinning, but all-out hard and fast
4th = really slow hard gear, still going all-out, but building muscle strength
5th = faster spinning, but all-out hard and fast

When I commute (5-7 miles each way, depending on the route, I tend to use the ride home as the hard ride. Another thing to do if there are rolling short hills is to plan to go hard and fast up the hills, and recover on the down hills.

One thing to keep in mind with intervals, is that the reason they work is based on going hard quickly before you are fully recovered, which forces your body to adapt. This makes them hard, because there is a cumulative effect of tiredness. So a 30-second all-out sprint, followed by 5 minutes of recovery before the next spring, will not give you the same effect.