I think that it would make sense for there to be a reduce/fold method in jQuery. There is already an each and a map, and I think that reduce makes sense for pulling data from the DOM. It would allow for something like this:

total = $(".prices").reduce(function (a, b) { return a + b.text() }, 0)

I understand that this can be done by using multiple libraries (ie. Underscore and jQuery), however given all of the other methods which are available through jQuery (ie. map, each, filter, etc.) this does not seem to be outside the scope of this library.