middleware.js

var forms_lib = require('forms')

module.exports = function(forms) {
    forms = forms || {};
    
    return function(req, res, next) {
      
      if (!req.session) {
        next(new Error("Forms middleware requires connect.session middleware to work properly"));
        return;
      }
      
      req.forms = {
        get: function(name) {
          var temp = req.session.forms && req.session.forms[name]
          if (temp) {
            delete req.session.forms[name]
            return temp
          }
          else return forms_lib.create(clone(forms[name]))
        },
        update: function(name, form) {
          req.session.forms = req.session.forms || {}
          req.session.forms[name] = form
        }
      }
            
      next();
    }
}

function clone(o) {
  if(typeof(o) != 'object') return o;
  if(o == null) return o;
    
  var newO = new Object();

  for(var i in o) newO[i] = clone(o[i]);

  return newO;
}

usage.js

var _ = module.exports = express.createServer(
  connect.cookieDecoder(),
  connect.session(),
  require('./middleware/forms')({
    invite: {
      email: fields.email({required: true})
    }
  })
)

_.get('/', function(req, res) {
  res.render('index', { locals: { form: req.forms.get('invite').toHTML() } })
})

_.post('/invite', function(req, res) {
  req.forms.get('invite').handle(req, {
    success: function(form) {
      var email = form.data.email
      db.save('invites', email, { email: email, date: +new Date })()
      req.flash('info', "Thanks for your interest, " + email + "!")
      res.redirect('/')
    },
    other: function(form) {
      req.forms.update('invite', form)
      res.redirect('/')
    }
  })

})