QuickSSO is a powerful and easy-to-configure cross-domain Single-Sign-On solution. The server is implemented by J2EE, but it does not restrict your develop language. You can add your application to SSO not only B/S application but also C/S one.
The project is being migrated to http://code.google.com/p/ciform...
IMPORTANT : The project is now being hosted at http://code.google.com/p/ciform
Plug'n Auth is an API providing easy integration of different authentication mechanisms into web applications. Within a few steps web admins will be able to change both the authentication backend and the logon frontend at any time with no further effort