Best free resource for learning advanced batch-file usage?

Question

What are the best free resources for learning advanced batch-file usage?

Answer 1

To get help on commands, this .bat file will put all commands' help into a nice HTML page: http://www.robvanderwoude.com/files/allhelp.zip

This guy has some other interesting .bat things as well. http://www.robvanderwoude.com/batexamples_a.html