gistfile1.txt

app.get(/^\/foo\/(.+)/, function(req, res) {
  var encoding = (/[.png]+$/.test(req.params[0])) ? 'binary' : 'utf-8';
  var path = '/foo/'+req.params[0];
  fs.readFile(path, encoding, function(err, data) {
    if (err) {
      throw err;
    } else {
      res.contentType(req.params[0]);
      res.send(data);
    }
  });
};