The OpenID foundation this morning announced that Microsoft, Yahoo!, Google, VeriSign and IBM have all joined the Internet OpenID initiative.
OpenID is an initiative where individuals can create one identity (and log-in) to be used on numerous websites across the web. It provides for other 'sharing' vehicles as well.
Over the past three months or so, several companies began supporting and implementing OpenID. This announcement adds a variety of significant players to the fold.
A good primer for developers for OpenID was posted by AOL in September here.
The announcement this morning from the OpenID foundation, along with recent updates, current developer info and more, can be found at the OpenID website here.