OpenID is getting a lot of good press lately - and rightly so.
OpenID goes some way to solve a number of problems, most notably authentication (remembering multiple user names and passwords for websites). Its basically a solution that allows you to forget about a myriad of usernames and passwords and have one webpage which controls access to all other OpenID enabled sites.
Microsoft tried to solve this problem years ago with their Passport solution - to limited success. Why? Nobody wants to trust their personal data to BIG businesses and be beholded to them. OpenID solves this problem by allowing you, the user, to create your own unique identifier (just like a web page) and host it yourself. However, if your not technically minded you can subscribe to one of many free /paid for OpenID service providers who will do all of the hard work for you.
Why should you look into this?
A number of reasons.
If your fed up remembering countless user names and passwords, or more importantly you want to control the data that websites own about you - OpenID is worthwhile looking at.
If your a web developer building an online community / web application you need to seriously think about OpenID as part of your authentication model to enable a greater number of people to access your service or to stand out from the current "me too" applications out there.
More importantly, using OpenID with items such as Microformats can open up interesting and exciting possibilities. I'll be talking about Microformats in a couple of days time :-)
Where to find more information: