How can I set the login page for registered users?

I set up a new blog at dodaddle.com and have is set so folks have to be logged in before they can leave a comment. When I tested this it worked fine, but during the log in the default page it takes you to is teh admin area. What I would like is for it to take the person back to the comment they wanted to leave a comment to, if that isn’t possible I would prefer defaulting them back to the homepage rather than the admin area.

Also, is there a plug-in similiar to community builder for Joomla?