WARNING

The Google Feed API is officially deprecated and doesn't work anymore!


No need for a whole plugin. This will return your RSS as a JSON object to a callback function:

function parseRSS(url, callback) {
  $.ajax({
    url: document.location.protocol + '//ajax.googleapis.com/ajax/services/feed/load?v=1.0&num=10&callback=?&q=' + encodeURIComponent(url),
    dataType: 'json',
    success: function(data) {
      callback(data.responseData.feed);
    }
  });
}

Use jFeed - a jQuery RSS/Atom plugin. According to the docs, it's as simple as:

jQuery.getFeed({
   url: 'rss.xml',
   success: function(feed) {
      alert(feed.title);
   }
});

For those of us coming to the discussion late, starting with 1.5 jQuery has built-in xml parsing capabilities, which makes it pretty easy to do this without plugins or 3rd party services. It has a parseXml function, and will also auto-parse xml when using the $.get function. E.g.:

$.get(rssurl, function(data) {
    var $xml = $(data);
    $xml.find("item").each(function() {
        var $this = $(this),
            item = {
                title: $this.find("title").text(),
                link: $this.find("link").text(),
                description: $this.find("description").text(),
                pubDate: $this.find("pubDate").text(),
                author: $this.find("author").text()
        }
        //Do something with item here...
    });
});