TheADONIS
The penis is NOT a muscle, it is a sponge. It cannot be "exercised" in order to make a muscle which does not exist bigger. There are exercises that enlarge the areas the blood flows to, over time you may posess an impressive weapon of ass destruction. There are a few ways to enhance what Mother Nature has sadly cheated you out of. plzchuckle is correct, besides, your fingers are always hard, and gaining impressive oral techniques will increase the sexual loyalty your cadre of female followers will have for you. I will say that girth provides more satisfaction for the majority of females, rather than length.
P.S. I'm an expert on teaching girls to squirt.