Register Users on Node Creation

These three modules attempt to solve essentially the same problem: encouraging site participation/content creation by lowering the barrier to entry. There seem to be two fundamentally different approaches to the problem:

• Session Method - This keeps users anonymous but continues associating new content to the anonymous user via sessions, eventually allowing a user sign up that associates all of his/her content with the new account if so desired. This is the type of system you see on sites like Stack Overflow.
• User Creation Method - This simpler approach attaches fields to a node creation form that, on submit, create an account for the user on the fly, associates the created content with the new account, and optionally logs the user into the new account. Ubercart does something very similar to this.

Whether you choose Inline Registration vs. The Sign Up Problem is up to you based on what your specific needs are.

Note that for Inline Registration, user experience could be greatly enhanced by using modules like Email Registration (to effectively hide the username field), Login Toboggan (to assign the user with a role of your choice), and Shared E-mail (to create new users for the same address) depending on your needs.

There is also Multiple forms module for D7. It's API module to merge more forms into one. I don't know how it set up because it has not-lame documentation.