I came across this today when trying to find an easier way to present a six-part form in a Rails project - a tabbed interface system built upon Prototype (an integral part of Rails). Called Control.Tabs it makes tabbed interfaces a synch to do: simply add an unordered list containing links to the blocks containing your to-be-tabbed content, and add a line of JavaScript to start the ball rolling - that's it! Some of the examples given on the site take it even further, including building an image gallery, and I've used it to build a series of form pages into one page complete with back/forwards buttons, all without refreshing the page. Good stuff, and well worth the time for any Rails developer to try using.