Cal Evans wrote a straightforward and excellent tutorial on how to to use Zend_Auth and its OpenID adapter to authenticate users today.  I was not only impressed by the tutorial itself, and I liked how he had code up front and so well commented, but also by how easy it was to implement the code here on my blog.  This was my first practical look at the Zend Framework, and the only gotcha I encountered was that it threw an Exception because I'd used session_start, but it provides its own classes to handle sessions. 

Unlike Cal, I did have luck in finding information on using AOL as an OpenID provider.  It was the first result when I googled for OpenId and AOL.  The short of it is that if you have an AOL IM account, you can login wherever you see OpenId, as on the sidebar here.   Heres what I'v been able to find about providers:

1. AOL - your Openid URL is of the form http://openid.aol.com/SCREENNAME, replace SCREENAME with your IM username.
2. Google - if you have a Blogger account, you have to enable it and then you can use your blog's url as an openid url
3. Yahoo! can provide openid, but you have to enable it.  The usability is pretty poor, as the first url it gave me as my OpenID identifier looked like  some weird hash token.  But you can chose an easier to remember one, or use your flickr url as an identifier if you have one.

There are more providers listed on openid.net.  If you have an account with AOL or Yahoo! and want to know what all the fuss is about regarding OpenID, try leaving me a comment!