I'll second the Carmichael Training Systems recommendation. You can download either whole workouts, or individual modules so you can create your own workout of any length. You don't need anything special - he really focuses on particular cadences, and you just work as hard as you want/need to at that cadence.

We're supposed to have a few more nice days, so I'm resisting the trainer as long as possible! (But it might be time to swap out the tires soon...)