jQuery keeps picking up speed. The lightweight (but with its plugins, apparently not feature light) javascript library is to be included in the next version of drupal and there appears to be some effort to provide rails helpers that will use jQuery rather than prototype.
That project will probably need to provide a drop-in replacement to convert me. Rails makes prototype use so very easy. But if it does, I’m sure I’ll be making use of my friend Karl’s recently announced Learning jQuery blog, which seems a great source of tutorials.