My jQuery plugin to parse query strings, including support for arrays and hashes. Also adds String prototype function.

jquery.parseq.js

(function($, undef){
  $.parseQuery = function(str){
    var obj = {};
    var soRegex = new RegExp(/\[(\S*)\]$/); // Test against sub objects / arrays
    $.each(str.replace(/^\?/, "").split("&"), function(i, param){
      param = param.split("=");
      var k = decodeURIComponent(param[0]),
          v = decodeURIComponent(param[1]);

      var m = k.match(soRegex);
      if(m){ // hash
        var k = k.replace(soRegex, '');
        if(m[1].length){ // subkey exists
          if(obj[k] === undef) obj[k] = {};
          obj[k][m[1]] = v;
        }else{ // No subkey, array object
          if(obj[k] === undef) obj[k] = [];
          obj[k].push(v);
        }
      } else{
        obj[k] = v;
      }
    });
    return obj;
  }

  String.prototype.parseQuery = function(){ return $.parseQuery(this); };
}(jQuery));