using xpath to select elements in jQuery?

Most browsers support document.evaluate() for selecting elements with XPath expressions - no jQuery required. The only major browser lacking support is Internet Explorer. Dimitri Glazkov has created a library that will implement the missing functionality for IE, however.

var result = document.evaluate("//a[@href='#']", document, null, 0, null),
    item;

while (item = result.iterateNext()) {
    // item will be an <a> element with href="#" here
}

You could easily create a plugin to wrap this functionality too:

(function($) {
    $.xpath = function(exp, ctxt) {
        var item, coll = [],
            result = document.evaluate(exp, ctxt || document, null, 5, null);

        while (item = result.iterateNext())
            coll.push(item);

        return $(coll);
    }
})(jQuery);

// And call it like so:
$.xpath("//a[@href='#']").click(function () { return false; });