Relax, what follows is confined to one species at a time. Most of the time, anyway.
Click here for the longest bird penis ever. Yes, there's a picture. I'll never look at ducks the same way again.
Dawn Olsen points to some guidance from the Ayatollah Khomeini on sex. This does involve animals. The four legged kind, even. There's more here and elsewhere on the site.
I think I've mentioned Dr. Tatiana's Sex Advice for All Creation before. The shtick here is that various species write in to Dr. Tatiana to ask for advice about dealing with their dysfunctions. And they have some unique, uh, situations, such as species of fruit fly with sperm longer than they are themselves.