All About The Penis - Lots of free information on the Human Penis. There's also a clitoris site, but you have to pay. Smaller is more valuable in this case, one would think.
Puppetry of the Penis - Can you imagine taking your penis on the road for a roadshow of monumental proportions? People do. (They're having auditions, if you're of a like, um, mind.)
Penis - Wikipedia - Here's what you get when you try to get serious about the penis on the web.
The Authentic Women’s Penis Size Preference Chart - See how you or a loved one measures up to female preferences.
The Ideal Penis In History, By Each Obsessed Culture (NSFW)--"These days, the idea of just what the "ideal" penis is always the subject of a storm of opinions. Is it all about size? What about girth? Is circumcision a necessity, or can male members be just as desirable without it? The answers can differ radically between cultures and continents"
(A note about the penis picture up there. It was found in Pompeii and is now in display in Naples, in the Secret Room. An erect penis, to the Romans, was a good luck symbol related to its association with health and youth, so stop snickering.)
Excercise that schlong! See the Erotica Index.