[jQuery] How do you tie sortables into the back-end with ajax?

[cliff]

List sorter functionality is way cool, but isn't very useful unless I
can tie it into the back-end. How do I couple it with an ajax call to
make sure the change is conveyed to the server? Seems to me you need
to detect the drop and have it launch an ajax call with the dropped
object id and the id of the object above it. Or the id of the object
you are dropping the item on.