The UNIX Reference Desk -- A fairly extensive list of links to UNIX related materials.
UNIXhelp for Users -- An extensive hypertext help for UNIX users created at the University of Edinburgh.
Some mirror sites for this tutorials are listed below.
UNIXhelp for Users (Emerson Center, Emory University, Atanta, Georgia)
UNIXhelp for Users (Mississippi Center for Supercomputing Research)
UNIXhelp for Users (Teleport Internet Services, Portland, Oregon)
UNIXhelp for Users (Nova Southeastern University, Fort Lauderdale, Florida)
On line manuals and tutorials for Unix stuff, e.g., vi, and WWW.