Redirect after login from custom login block I have added the login form to a page using drupal_get_form.
Now, I would like to redirect the users back to that page after login.
Note: I don't want to redirect users that logged in somewhere else (e.g. user/login), and I also don't want to use a contib module for that.

B.T.W
Maybe if I'll Ajaxify the login form it will have the same effect?

I'll appericiate any help and/or examples. 

Thanks!
You have to add form_alter and add custom #submit handler to user_login form if current_path() is correct for you and set $form_state['redirect'] there.

Check this post Redirect to a custom page after a node has been added or edited.

Also it can be achieved via custom rule, if you don't want to write any custom code.