Here’s an excellent resource for getting a sense of what’s currently possible with OpenID. It’s a post from Sara Perez on ReadWriteWeb, with a breathtaking list of OpenID providers and “relying parties” (sites where you can use your OpenID).
While the skeptics remain, it is clear that there has been growing momentum for this critical building block of the Social Web, especially in the past few months.
I’d also recommend tapping into the wisdom of Joseph Smarr, who is both a passionate advocate of OpenID and an early implementer, as Plaxo’s chief platform architect. Plaxo rolled out support for OpenID late last year, becoming one of the first large-scale consumer sites to accept OpenID. And most recently, Joseph worked with Yahoo! on their implmentation, allowing users to log in to Plaxo with their Yahoo! credentials (using OpenID behind the scenes). Here’s an interview I did with him on the day of that announcement. It’s a good intro to the topic:
For developers with an interest in implementing OpenID, I recommend Joseph’s “A Recipe for OpenID-Enabling Your Site.”