Then I found myself in need of a GitHub account and repo to play with BountyOSS's progressing GitHub integration. A test repo would be boring, so I thought to myself "Hey, this federated avatar stuff is pretty neato, I'll do a repo involving that.". So I did.
And the result is clavatar.
If you're building some sort of site with users, and you want to add avatar support without having to host all those pesky images yourself, you can use clavatar to find an appropriate avatar URL for a given e-mail address or OpenID/URL. It supports libravatar-style federated avatars, Libravatar-as-a-service, Gravatar, and even Unicornify.
(clavatar:get-avatar-url "email@example.com" :size 120) ; => #<URI ...> (clavatar:get-avatar-url "http://example.com/user/avatars") ; => #<URI ...>
Most of the dependencies are readily available through Quicklisp, but you will need a more recent copy of iolib. And I do mean recent—the patch required for clavatar to work landed earlier today.