Email Login

This module allows users to login with either their username or the email address associated with their account. The module requires no configuration -- once installed, users can log in as usual with their username (the only noticeable difference is that the username textfield says "Username or Email Address:" rather than just "Username:") or enter their email address.

This module is similar to LoginToboggan and email_registration, although it is lighter weight and requires no configuration. If you're looking for a module to completely replace usernames, or hide them from users, this isn't it. It simply allows them to log in with either usernames or email addresses automatically.