Make your time in the gym count by choosing multi-joint movements over single joint ones. Engage larger muscles and replace single joint exercises (curls, tricep extensions, etc.) with multiple joint movements (pull-ups, dips, incline press, etc.) Focus your time on multi- joint movements and larger muscle groups (lats, shoulders, chest, hips, and legs) and your smaller muscle groups will get plenty of work (biceps, triceps, and abs).
This article by T-nation shows how pull-ups stack up to bicep curls of all flavors for activating the biceps. Not only are pull-ups a tremendous rear shoulder and back developer, but benefit the biceps to boot.