>> User activinty enhancement plugin

Hi guys. I wonder if anybody here knows a plugin that does the following.

I want users in my blog to be able to add posts post and register simultaneously. Here’s what I mean:

1. Any user can post to a blog. During the post he’s asked to leave his name and email
2. When pos is submitted, the user’s email gets automatically checked against the users database. If it’s found, the user is asked of his password, otherwise
3. An email confirmation link is sent to the user’s address. Upon confirmation a) user’s post gets automatically approved and b) user receives a welcome message with his generated password.

Did you ever meet a plugin with this or similar functionality?

Thanks!