Partial.js

Function.implement({
  partial: function(bind, args) {
    var self = this;
    args = $splat(args);
    return function() {
      return self.apply(bind, args.concat($A(arguments)));
    };
  }
});

// function add(a, b) {return a + b;}
// add.partial(null, 1)(2) -> will return 3