There is currently a test server setup at http://www.contrib.andrew.cmu.edu/openid/<andrew id>. This url is your OpenID. A nice way to test your OpenID is by logging in at http://www.livejournal.com/openid/.
Details
The test server is a hacked up version of phpMyId. The changes can be summarized as remove HTTP/Digest Authentication and replace it with a redirect to a WebISO-protected folder that contains a PHP script. This script sets the bits in the session to mark it as authenticated. There is probably a less brutish way to do this, hell if I know it.
Future
Easier to remember url (http://openid.andrew.cmu.edu/<andrew id>, e.g.)
Have user-editable details in a database (http://openid.net/specs/openid-simple-registration-extension-1_0.html)