A simple plugin that adds the gravatar photo associated with the user's email to their profile page... MultiSite compatable!
Nope, just upload and activate. There are not options, so the code'll do the rest.
A Globally Recognized Avatar - Your Gravatar is an image that follows you from site to site appearing beside your name when you do things like comment or post on a blog. Avatars help identify your posts on blogs and web forums, so why not on any site?
From the Gravatar.com website
To create your free Gravatar, visit Gravatar.com