The two popular centralized authentication systems, PAM and Kerberos, are supported in every well known unix-like and unix-based operating system (GNU Linux, *BSD, Solaris, HP-UX, mac OS X, etc). A search in google for "kerberos" and "Pluggable authentication modules" will return plenty of information sources on these projects.
If you tell us what exactly you need we might be able to point you to a better direction, since PAM and Kerberos are not really authentication methods rather than authentication systems, with the former used commonly on local authentication and the later providing a solid solution for secure authentication through a network.
At the user level they can both work with various authentication interfaces -what you are probably referring to-, like password prompts, smartcards or even biometric validators. The difference is that kerberos is just a protocol, requiring a unique software implementation for each purpose, while PAM is a standard system that can easily utilize and combine other systems (including kerberos) thanks to it's modular design.
