flow.js

function flow (generator) {
  var iterator = generator(next);
  next();
  function next (err, result) {
    if (err) iterator.throw(err);
    var item = iterator.next(result);
    if (item.done) return;
    if (typeof item.value === 'function') item.value(next);
  }
}

usage.js

// hacks, disregard these
var fs = {
  readFile:function(a,b,c){
    setTimeout(function(){
      console.log('foo', a);
      c();
    },1000);
  }
};
 
function read (path) {
  return function (done) {
    fs.readFile(path, 'utf8', done);
  }
}
 
// usage!
flow(function* (next) {
  var a = yield read('Readme.md');
  var b = yield read('package.json');
  console.log('wait for it...');
  var c = yield setTimeout(next, 1000);
  console.log(a);
  console.log(b);
});

Take a look at https://github.com/visionmedia/co