climbing: more than quads, more than leg
Please don't just focus on quad strength. Even if you're climbing out of the saddle, you pull the pedals up with your hamstrings & glutes. For a seated climb (which suits most riders), push back in the saddle & drive with your hamstrings & glutes. I feel that flat terrain burns the quads & hills burn my hamstrings & glutes.
Now for some secret weapons:
Road cyclists are taking a cue from dirt riders & working on upper body strength.
Core (torso) body strength is essential to strong climbs. So make stablization work a part of your fitness routine (Pilates, a fitness ball, Cathe's killer planks, etc.). Power Hour & S&H have a lot of stabilization work (forward tilts, etc).
Ultimately, the only way to climb strong is to ride a lot of hills. On the bike:
Hill repeats! Up & down, staying aerobic (not anaerobic) while climbing. I do 4-7 repeats on a moderate hill, then climb a very steep hill (in my granny gear) to finish.
Check your breathing when climbing. If you're not breathing from the diaphram, you've got some more off the bike work. Try some Tai Chi, yoga or Pilates.
It's a lot isn't it? But it's such fun to spin past others on the way up a hill!
Debra