Are you sick of keeping track of separate user names and passwords for every site on the Internet? You're not alone.

We might not have to stand for that nonsense much longer. Single sign-on is coming soon to some of the biggest names in the online world.

Yahoo! (Nasdaq: YHOO) just threw its support behind the open-source, Internet-based OpenID 2.0 digital identity standard. By the end of January, you can sign up for the public beta program and start using your Yahoo! ID across more than 9,000 sites. Adding 248 million Yahoo! users to the 120 million accounts today will more than triple the current OpenID user base.

There are plenty of recognizable names on the guest list already, including Microsoft (Nasdaq: MSFT), Sun Microsystems (Nasdaq: JAVA), Novell (Nasdaq: NOVL), Digg, Technorati, WordPress, and Zooomr. And as you'd expect, the rumor mill is running hot right now, hinting that Google (Nasdaq: GOOG) and IBM (NYSE: IBM) might join the party soon.

The usability implications are tantalizing. Imagine using your Yahoo! ID to sign in to Microsoft Live, GMail, or the SunSolve Solaris support site. OpenID provides the secure authentication, and then it's up to each site to check whether you're authorized to see its content.

If this works, we'll be able to check our email, balance the checkbook, and apply for Turkish citizenship with a single online identity. One username. One password. That's all it takes.

That's obviously a pipe dream now, and we're many years away from a full-scale global implementation of this, or any other, sign-on protocol. I, for one, can't wait to chuck the nearly unmanageable collection of unguessable passwords that a 21st-century digital boy collects over half a lifetime.

The token-passing authentication method is battle-tested, secure, and anonymous to the destination site -- and that's why we'll still need to set up accounts with every service but with a single point of contact for logging in. Change your password once, and you've changed them all.

When online life becomes that easy, there'll be one less reason for the average couch potato to feel intimidated by the Internet. Anybody can remember just one set of credentials, right?

There are lots of single sign-on solutions on the market today, including products from OpenID partners like Microsoft, Sun, and VeriSign (Nasdaq: VRSN). I just love to see traditional rivals pulling together toward a common goal. This platform may not win the race, but you can bet that Google and Yahoo! will support whichever one does win. This is a great head start for OpenID, if nothing else.

Hey -- will the OpenID consortium ever go public?

Further open Foolishness:

Yahoo! is a Motley Fool Stock Advisor recommendation, and Microsoft is a Motley Fool Inside Value pick. Either newsletter is available for a free, 30-day trial.

Fool contributor Anders Bylund is a Google shareholder with a background in single sign-on support, but he holds no position in any other company discussed here. You can check Anders' holdings if you like, and Foolish disclosure won't even ask you to log in.