Update: Added review of VeriSign's offering below. As Kelly mentioned yesterday, I have spent a few hours looking at how other sites have implemented their OpenID interfaces. Yahoo!'s new service was my favourite because it explains everything and makes it very clear and simple. On the other hand it lacks some features that I think are essential. Identity providersYahoo!
least features (cannot 'remember' authenticated sites)
lots of useful explanatory text
login to the service with the standard Yahoo! login screen which benefits from anti-phishing protection
doesn't ask to reconfirm registration details, upon returning to the site you are already registered & ready to go
Conclusions Yahoo! has done an excellent job at making OpenID easier to understand for less techy folks. Plaxo has probably the best implementation of an OpenID consumer. VeriSign demonstrates the use of advanced security features as well as improved phishing detection using a browser extension. Directed identity in OpenID 2.0 affords a much improved user experience. Instead of remembering an arbitrary URL such as me.yahoo.com/something, users need only remember the URL of the identity provider, in the case yahoo.com. Everything else happens behind the scenes. Few sites currently support OpenID 2.0 and there is no way of tellin, at sign-in, which version of OpenID the relying party supports. This will undoubtedly create confusion especially since OpenID 2.0 support does not guarantee OpenID 1.1 support. The recommended option is to support both versions.