app.coffee

express = require 'express'
assetManager = require 'connect-assetmanager'

app = express.createServer
app.use assetManager

app.js

var express = require('express'),
  assetManager = require('connect-assetmanager');

var app = express.createServer();
app.use(assetManager);

gistfile1.txt

$ coffee app.coffee

TypeError: Object function (options){
  if ('object' == typeof options) {
    return new HTTPSServer(options, Array.prototype.slice.call(arguments, 1));
  } else {
    return new HTTPServer(Array.prototype.slice.call(arguments));
  }
} has no method 'use'
    at Object.<anonymous> (/.../app.coffee:6:7)
    at Object.<anonymous> (/.../app.coffee:7:4)
    at Module._compile (module.js:402:26)
    at Object.run (/usr/local/lib/node_modules/coffee-script/lib/coffee-script.js:62:19)
    at /usr/local/lib/node_modules/coffee-script/lib/command.js:120:29
    at /usr/local/lib/node_modules/coffee-script/lib/command.js:90:26
    at [object Object].<anonymous> (fs.js:107:5)
    at [object Object].emit (events.js:61:17)
    at afterRead (fs.js:878:12)
    at wrapper (fs.js:245:17)

$ node app.js

(no errors)

So the problem was that the CoffeeScript was translated to:

 var app = express.createServer;
 app.use(assetManager);

And of course it wouldn't work, because app was the createServer function, not it's return value. To fix: add parenthesis after createServer (and any other method call that doesn't have any parameters, because CoffeeScript compiler can't determine what you want then)