User registration for blogs

Hello,

How can a blog allow user registrations on their site? Is there a plugin for this? When I click on "Register" from a blog it take me to the Sitewide "create a blog". It goes to (for example) http://blog1.mainsite.com/wp-login.php?action=register which then redirects to the wp-signup.php

I was looking at plugin WP Blog Registrations plugin among the free plugins you have.

Thanks.