Backbone.js is an interesting project that provides a real backbone structure for more complex JavaScript projects. It implements the Model/View/Controller structure for JavaScript and provides a number of Collection classes with corresponding APIs. What it does not provide is a thick stack of UI stuff or the 1001st implementation of DOM navigation or similar - it should therefore work well with things like jQuery, as it actually only provides the basic structure on which one can build when one no longer wants to store everything in the DOM. However, there are already some overlaps, for example with events - these are also provided by jQuery, but here they are not bound to DOM nodes, but to arbitrary objects.