Best strength exercises for improving bike speed

I'm trying to incorporate 2 or 3 days per week of strength training into my off-season program. What are some good strength training exercises for improving my bike leg? Still a newbie, averaging about 17 mph in training and races. It is constantly my weakest link.

I don't have a gym or any weights heavier than 15 pounds, so keep that in mind I guess. Any recommended drills to help speed me up in the offseason and maybe approach that magical 20 mph barrier?

Edited by apw0397 2005-10-11 2:34 PM