[ale] Enterprise Authentication

[hbbs at comcast.net (Jeff Hubbs)]

What's the thing to use for managing user authentication in mixed
Windows/UNIX/Linux environments these days?

I'm familiar with:
  
  LDAP
  Kerberos (isn't MS' implementation broken?  What are the issues?)
  MS Active Directory (is that MS-only?  if not, too risky to use?)
  Some Sort of Novell Product
  Some Sort of [probably abandoned] Banyan product

Whatcha think? 

- Jeff