Django Hijack
With Django Hijack, admins can log in and work on behalf of other users without having to know their credentials.
Docs
See http://django-hijack.readthedocs.org/en/stable/.
Testimonials
I am using django-hijack on a project with hundreds of users, wonderful tool for support. Thank you!
-- benzinonapoloni on reddit
This is a super useful tool. I have a site where I occasionally impersonating users to help troubleshoot their issues. This is a huge time saver.
-- orangishyellow on reddit