Universal JavaScript Module, supports AMD (RequireJS), Node.js, and the browser.

universal-module.js

(function (name, definition){
  if (typeof define === 'function'){ // AMD
    define(definition);
  } else if (typeof module !== 'undefined' && module.exports) { // Node.js
    module.exports = definition();
  } else { // Browser
    var theModule = definition(), global = this, old = global[name];
    theModule.noConflict = function () {
      global[name] = old;
      return theModule;
    };
    global[name] = theModule;
  }
})('myModule', function () {

  // return the module's API
  return {};

});

usage.js

// AMD
require(['path/to/myModule'], function (myModule){
  // use myModule here
});

// Node.js
var myModule = require('myModule');

// Global
myModule
// if myModule is already defined, `noConflict` gives it back
var myNonConflictingModule = myModule.noConflict();

I'm playing around with a format here: https://gist.github.com/1262861

It puts most of the nasty adapter stuff at the bottom, so readers of the code can focus first on the module's capabilities and not the registration boilerplate. It is a bit opinionated though.