How to allow login and registration of visitors without leaving the frontend?

Hi,

I just bought Q&A and configured the CSS and it seems to work very well. But I have one problem: my visitors need to register in order to make questions. So I need the registration and subsequent logins to be as simple as possible.

Right now when a visitor tries to submit a question he is redirected to the normal Login/Registration pages which then sends them to my backend administration.

How can I have my users login and register without ever leaving the frontend?
Also, which plugin do you advise to use for integration with Google Accounts, Facebook, etc?

My url: http://dev.abapinho.com

Thanks in advance,
Nuno