The American Sign Language University offers both ASL I and ASL II on their site, free. Each course equals .5 credit for American high school, 6 CEUs, or 4 University semester hour credits.
This is a simply created course. It may not be the best one out there (can you recommend another free one?), but it’s a place to start. This course does not require registration…you may get started right now, if you like.