NFS/NFS+ network filesystem
 
  Wikipedia :  Network file system (protocol)
               Open Network Computing Remote Procedure Call

  Current version 4 
  
  Originally developed by Sun for Solaris systems.

  Based on Open Network Computing Remote Procedure Calls.

  Uses TCP connections.

  Allows system to share specified filesystem partition of the network.
    see /etc/exports on system being shared.

  Uses server on system being shared to accept requests and provide access
    to shared filesystem.

  Result is somewhere between a hard and soft link.

  Provides a high degree of authentication and security.

  Primarily between Unix systems but versions available for Mac, Microsoft,
     Novell, IBM AS/400.

  * Example : we run nfsd (nfs server) on both turing and hopper, which 
    allows users to log into either system and still see/use their home 
    directory.

    Also, your web directory is nfs mounted from another system.
  
NIS/NIS+ 
  Network Information Service
  (Originally callled Yellow Pages server, so most commands start with yp)

  Used to provide information about users access resources across the network,
    commonly through NFS.

  Information such as user authentication, password authentication, home 
    directory, mail aliase, etc.

  Similar but more complete than a DNS server, can even provide the same 
    information in some cases.

  NIS+ - adds encryption and other better security. 
  

LDAP - Lightweight directory access protocol.
  Alternative to NIS (more OS and implemention generic)
    Protocol that is left up to the user to implement with tools at hand. :)

  Protocol that describes a virtual directory structure that can cross
    partitions, drives, networks.

  Protocol has ability to describe an unlimited number of attributes for 
    a file.

  Protocol is independent of software/hardware it is actually implemented on.

  Microsoft's Active Directory is built on top of the LDAP protocols.

Samba
  wikipedia  Samba (software)

  Alerntative to NFS.

  Based on the open SMB/CIFS protocol (implemented on top of). 
    - Server Messsage Block / Common Inernet File System

  Primarily designed to access Unix filesystems and print services 
    from Windows/PCs.

    Compatible with MS Active Directory.

    Servers run on GNU/Linux, Solaris, AIX, BSD, Mac OS X
 
  We use Samba on the department web server to allow our staff to access/edit
    web pages through the Windows folder evironment.