Anyone that uses the web a lot no doubt has a multitude of different usernames and passwords for different sites.
Even if you try to use the same credentials across the board no doubt there will be exceptions when you want to choose something more secure or when your favoured username is already taken. It's these multiple log-in credentials that are soon to be a thing of the past with the introduction of OpenID, which seems to be gathering momentum.
So what is OpenID?
OpenID is an open, decentralized, free framework for user-centric digital identity.
Essentially, OpenID will provide users with a single digital identity. So instead of having log-in details for every site you visit you can log-in to each site using a single OpenID. From a users perspective this is achieved by first creating an OpenID with a provider such as claimID (sadely claimID has now closed). You are then provided with a unique URI which points to your OpenID. This is then entered into any sites where you want to log-in. Rather than delve into minute detail I would recommend taking a look the OpenID screencast by Simon Willison.
OpenID is being (or has already been) adopted by the likes of Microsoft, Verisign, digg.com, AOL, Yahoo!, LiveJournal, Zooomr, Wikitravel and ma.gnolia.com to name a few.