This is a tool to test Authentication on websites. It will show what authentication type is used: Kerberos, NTLM, basic, none. But it also shows other information like: SPN used, HTTP headers, decrypted NTLM and Kerberos authorization headers. And it can also show and delete your Kerberos Tickets.
See this post for more details and screenshots: http://blog.michelbarneveld.nl/michel/archive/2009/12/05/kerberos-authentication-tester.aspx
Thanks for the tool. Helped me a lot verifying that authentication is setup and working