Have you considered Cfengine?

Cfengine is an automated suite of programs for configuring and maintaining Unix-like computers. It has been used on computing arrays of between 1 and 20,000 computers since 1993 by a wide range of organizations.

Cfengine was implemented primarily on Unix-like operating systems, but has since been ported to Windows operating systems and MacOS X.

I have used it myself in test and develepment environments for maintenance, primarily making sure I have all the required software installed in advance, the directory structures is in place, accounts are set up etc. This incredibly powerful tool is released under GNU GPL.

Update:Added platform section from the reference.