I know that it's best to let sleeping nodeshells lie, but I raise snakes and snake sex is actually pretty darned interesting.
Male snakes have two penises called hemipenes. They usually twine themselves around the female of the species and insert a hemipenis into the female's cloaca. From there the male fires up some Barry White music and the pair does what just comes naturally. There are rare reports of a male snake copulating with two females at once, but as it is with males of the human species, he usually has trouble satisfying one woman and doesn't bother with two.
Certain species of snakes, such as boas, are also some of the few reptile species capable of giving birth to live young.
I'm just kidding about the Barry White thing, as far as I know.
Update: kthejoker has pointed out that anacondas participate in huge orgies in which around ten males will copulate with one female. This increases the odds of insemination. The August National Geographic has confirmed this.