We are still investigating the options, but OpenAuth seems like a pretty useful open and applicable standard for authenticating users. In the book, we are trying to build up a series of guides on useful tools and toolkits for doing things.
So I'd also like to read about the pros and cons of the various authentication packages.
I couldn't spot an issue discussing it, but if you have a good link on the pros and cons, I'd love to see it. :)