SSO solution for Java based web application

Hi, This time I'll keep the post simple, I would just like to recommend the open source java based solution for the single-sign on.
Recently I've had a chance to fiddle with SSO related stuff.
I've chose an outstanding piece of software called CAS
This software provides a simple yet powerful solution for the SSO and implements a lot of different methods of performing the authentication.
I would like to mention that they have a very supportive community, they helped me a lot in resolving some technical issues.
In just a couple of days I was able to come with SPNEGO based solution for the web environment that works against kerberos system.
Although this product seems to be more widespread in the academics, it seems to be really mature and up-to-date.

So, I definitely recommend to consider CAS for the sso related stuff.