Timing

This is probably the most often touted benefit of leg shaving, shaving time off of a race. However, the advance you gain in aerodynamics is so incredibly slight that you would probably only notice this in a time trial on on the track as opposed to a road race.

Healing

Ah, road rash. Every cyclist will eventually experience this "joy" of cycling after a nasty fall. The presence of hair on the legs makes cleaning the wound more difficult. It can also increase the chances of infection.

Massage

Many cyclists are found of massage. Massage is reportedly less painful for those without leg hair and easier to perform, though we all know men and women who don't shave their legs and still receive massages.

www.bicycling.about.com