Samba Team member John H. Terpstra has written an overview of ACLs for the system administrator dealing with both Windows and Unix (through Samba, of course). The article can be found on searchenterpriselinux.com and is a nice outline of the differences between Unix file system permissions and Windows' ACLs. Those looking for an accessible and understandable introduction to the topic should check out John's piece.

From the abstract:

The parallel to this is that the Windows networking engineer will solve all file and directory access challenges with Windows ACLs, and the UNIX administrator will find this predilection both unnatural and awkward. Despite these opposing perspectives it is necessary to deal with them in an environment where Samba is used to provide Windows file and print services.

For more, please see Samba-3: Windows file and directory ACLs.