If you want to customize the login and registration process of your Drupal site, chances are, you're looking for the LoginToboggan module.

This series covers all of the ways you can modify the registration/login process without having to write your own code.

Some of the features include:
* Allowing users to login using their username or their email address
* Allow users to create their password at registration, instead of having to wait for a confirmation email
* Users are logged in immediately after account creation, and granted a role with limited permissions until they authenticate their account
* Redirect users to specific pages after account creation and confirmation
* Display the login form on access denied pages
* We'll also use Rules to send a welcome email to users once they have authenticated their account.

It's a great tool that you can use to customize the user flow on your Drupal site.

Check out the LoginToboggan series here.