I recommend that nobody takes you up on your offer. I expect your intentions are good, but you must realise that by attempting penetration testing without the proper legal documents in place, users of this forum could land themselves in trouble.
Because we've no guarantee that that is in fact your own web site, never mind having explicit permission to attack it, we cannot legally do so.
If you want someone to pen-test your application, whether for free or paid, I recommend that you have a contract in place which states exactly what they're allowed to do, when, and something which lets them verify that you do indeed have the proper authority to authorise such an action.
Mark