This Spotted Leopard Slug is not from the U.S., but since it was introduced it has spread. According to Oregon State University, it moves a lot faster than the native banana slug (the picture in the banner above on Slugyard). This speed helps it catch other slugs for a tasty (ugh) meal.
See the hole in its side? This is called a pneumostome, and it is used by slugs to breathe. For more information on slug anatomy, click this link to check out another OSU website.