Masquerade Module

The Masquerade module allows site administrators (or anyone with enough permissions) to switch users and surf the site as that user (no password required). That person can switch back to their own user account at any time.

This is helpful for site developers when trying to determine what a client, logged in as themselves, might see when logged into the site.

NM EPSCoR discovered this module after launching their live reporting reporting site in June of 2013. The module has proven to be invaluable in testing what various roles can see when they are logged in.

Download it here:
https://www.drupal.org/project/masquerade