Authentication for clusters

Hi,

 I am new on the list but not new with Bioclusters. I am trying to
setup an authentication system for our 64 node cluster that integrates
with our web services (all Apache/PHP based) and our desktop management
(mix of XP, Mac OS X and Linux). At the moment there's no authentication
platform for any of these (other then local files). Is there a
commercial solution that you might recommend that integrates
authentication among all these plaforms ? I checked on Vintela and
Novell but I wanted to know what other people are doing. I could just
run a secure OpenLDAP but its management tools leave much to be
desidered and our management prefers commercial tools for businees
continuity purposes. 

Any ideas ? Thanks much,

Luigi--