'connect's "vhost" middleware, modified to accept a generic handler function. Works well with "stack".

example.js

var vhost = require('vhost');
var stack = require('stack');

var foo = function(req, res) {
  // Do something...
}

var bar = function(req, res) {
  // Do something else...
}

var handler = stack(
  // Only for top-level 'foo.com'
  vhost('foo.com', foo),
  // For all subdomains at 'bar.com'
  vhost('*.bar.com', bar)
);

var server = require('http').createServer(handler);

package.json

{
  "name": "vhost",
  "description": "'connect's \"vhost\" middleware, modified to accept a generic handler function. Works well with \"stack\", \"connect\", and \"http\" servers.",
  "tags": [
    "vhost",
    "connect",
    "stack",
    "http",
    "server"
  ],
  "version": "0.0.2",
  "repository": {
    "type": "git",
    "url": "git://gist.github.com/820042.git"
  },
  "homepage": "https://gist.github.com/820042",
  "author": "Nathan Rajlich <nathan@tootallnate.net>",
  "main": "./vhost.js",
  "engines": {
    "node": "*"
  },
  "directories": {},
  "files": [
    ""
  ]
}

vhost.js

// Modified from "connect" to work nicely with "stack", "connect" or the regular "http" server.
// Pass a regular 'handler' function instead of a 'server' instance.

module.exports = function vhost(hostname, handler){
  var regexp = new RegExp('^' + hostname.replace(/\./g, '\\.').replace(/[*]/g, '(.*?)') + '$');

  return function vhost(req, res, next){
    // In the case of a regular 'http.Server', there will be no 'next', so define one just in case
    next = next || function() { res.writeHead(404); res.end("Not Found"); };
    // An HTTP/1.0 request won't have a 'Host' header...
    if (!req.headers.host) return next();
    var host = req.headers.host.split(':')[0];
    if (req.subdomains = regexp.exec(host)) {
      req.subdomains = req.subdomains.slice(1);
      handler.call(this, req, res, next);
    } else {
      next();
    }
  };
};

fyi, this should be updated with some bugfixes from connect-vhost - notably that the regex should be case-insensitive