$(function(){
  $.ajax({
    url:'aaaaaaaa.json',
    dataType:'json',
    success: function(data){
      for(var index in data.channel.item){
        var title = data.channel.item[index].title;
        var link = data.channel.item[index].link;
        alert(title + '  > ' + link);
      }
    }
  });
});

【RSSをJSON形式化したサンプル】 aaaaaaaa.json
{
    "@attributes": {
        "version": "2.0"
    },
    "channel": {
        "description": "xxxxxxxxxxxxxxxxx",
        "item": [
            {
                "enclosure": {
                    "0": "",
                    "@attributes": {
                        "length": "133",
                        "type": "image/gif",
                        "url": "http://www..............."
                    }
                },
                "guid": "yyyyyyyyyyyyyyyyyyy",
                "link": "http://www...............",
                "pubDate": "-",
                "title": "zzzzzzzzzzzzzzzzzzzzzzz"
            },
            {
                "enclosure": {
                    "0": "",
                    "@attributes": {
                        "length": "133",
                        "type": "image/gif",
                        "url": "http://www..............."
                    }
                },
                "guid": "yyyyyyyyyyyyyyyyyyy",
                "link": "http://www...............",
                "pubDate": "-",
                "title": "zzzzzzzzzzzzzzzzzzzzzzz"
            },
            {
                "enclosure": {
                    "0": "",
                    "@attributes": {
                        "length": "133",
                        "type": "image/gif",
                        "url": "http://www..............."
                    }
                },
                "guid": "yyyyyyyyyyyyyyyyyyy",
                "link": "http://www...............",
                "pubDate": "-",
                "title": "zzzzzzzzzzzzzzzzzzzzzzz"
            },
            {
                "enclosure": {
                    "0": "",
                    "@attributes": {
                        "length": "133",
                        "type": "image/gif",
                        "url": "http://www..............."
                    }
                },
                "guid": "yyyyyyyyyyyyyyyyyyy",
                "link": "http://www...............",
                "pubDate": "-",
                "title": "zzzzzzzzzzzzzzzzzzzzzzz"
            },
        ],
        "language": "ja",
        "link": "http://www...............",
        "pubDate": "-",
        "title": "xxxxxxxxxxxxxxxxx"
    }
}