squats, straight-leg deadlifts, front squats, powercleans...all of these have given me more strength for kicking steps; I've noticed significant gains.
For me, lifting has helped me maintain good strength and core conditioning over the winter and shortened the time it took me to get back to climbing where I was last fall (or close to it, anyway). I do legs one day, lats/delts another, biceps/triceps after that, chest next...or a variation of that schedule. One nice thing to bring on the pain is stacking exercises; by that I mean on bicep/tricep day, do ALL your bicep lifts in sequence, THEN do all your tricep lifts. Man, you'll feel that. Helps with endurance, too.