"There are a number of ways to invite Linux, UNIX, and OS X to the Windows Server Active Directory party. The operating systems we use today will interoperate in many ways because each includes some level of common protocol support. Support for HTTP is an obvious protocol they all share. SMB is also commonly used for access to Windows file system shares. In the UNIX world, NFS ruled the ether for years. Thankfully directory and security protocols like LDAP and Kerberos have also become common in the desktop and server operating systems."
Watch a 3 episode series of helpful how-to screen casts on Keith's blog.