Services_Libravatar is a PHP5 library to the Libravatar service that delivers avatar pictures to other websites: It gives you image URLs for email addresses.
Libravatar offers several benefits over the classic Gravatar service: It is federated - you can host the avatar server for your mail addresses yourself. It is open source. It can fall back to Gravatar if Libravatar does not have a picture for the email address, making it perfectly backwards compatible. It allows you to give a picture to your OpenID.