OpenID has been getting more and more famous and many OpenSource projects have already adopted it ...
There are libraries for the most common programming languages (Python, Ruby, Java, Perl, .Net)
How does it work?
Get an OpenID userid from an OpenID provider (wordpress.com, aol, livejournal,.. OpenIDServers) or from your own provider OpenID (see Run_your_own_identity_server, i.e crowd is used by several big companies but you have to pay for it if you use it not for openSource projects)
and then you can use that account (if you want) to enter all other OpenID enables sites (https://www.myopenid.com/directory)