Integrating Open ID into your website opens your site to a growing number of Open ID users. Leveraging digital identity simplifies user signup and login and can even allow you to no longer need to save user information on the server.
There is a $5000 bounty available for open source projects that integrate Open ID. Read about it here and get paid.
The Apache Heraldry project maintains a repository of source code for libraries for and implementations of Open ID. Signing up for the Mailing Lists will keep you current on the most recent changes in digital identity.
The OpenID spec and Yadis spec are essential reading for successfully implementing digital identity.