1) get a job at the top of a mountain, get a house at the bottom, bike commute.
-- seriously though, try to ride with more intensity and with less emphasis on cardio, try to go up hills in a higher gear than you normally would, but not so high as to cause knee pain.
2) weight lifting? get a book on building lower body strength?

3) SUBWAY! EAT STEAK! -- seriously though, higher protein diet could help, or your same diet with some protein supplements. personally i'd rather eat beef, chicken, turkey, fish, soy, nuts than to drink those powdery protein shakes and pills.

4) cross train. perhaps swimming or running could help. or you could go mountain biking, around here our mountain trails are much much harsher than our roads, and will thus build you up faster.