I noticed that there was some interest on the Dreamhost forums for AJAX to register for lists. I thought this was a good idea, and upon finding no solution, I set out to make one.
I admit that both this is not terribly easy to set up nor is it terribly hard. You have to modify 1 php file and include the required components on your web page. There is a full readme enclosed to help you get it set up.
If you have any questions or comments, please leave a comment!