AIA Layer Name Standards  A really good website for links to all the best training sites.

myCADsite             Excellent FREE Autocad Tutorials at all levels

Affralisp                  One of the best Autolisp sites

CADTutor               Excellent tutorial site

Jeffery Sanders       Great Autolisp site.

JTB World                 Great Autolisp site.

ENGDS                  Examples of Lisp routines

CADforum          List of Autocad commands

Attila G Horvath    Good a description of the new Autocad Command line and other stuff.

Novedge     Is Autocad still relevant 

DesignSpark Mechanical A great free 3D modelling program


The Ascii Codes

US National Layer  Standard   Designer Hacks summary Layer Manager Tutorial One of the best Layer tutorials on the web

Center for the Study of Architecture (Archeology) If you really want yo see how complex Layer Names can become