Single Sign-on

Lately I started seeing one of the project requirements is “Single Sign-on”. Though Single Sign-on is great feature, is it possible in all the cases? Here is my understanding on Single Sign-on.

You have different intranet applications and instead of doing authentication and authorization for each application, do the authentication only once and pass the authentication ticket to all the applications and it is up to each of the application to do their own authorization.

If you want do this in your intranet environment with web applications, it is easy enough with your windows authentication and LDAP.Similarly, if you want to do this in internet environment with web applications, it is possible with Passport services. What if I want to use couple of intranet web applications with couple of client/server applications (written in Delphi or Powerbuilder)? Has anybody done like this?