BASH commands
http://www.bash.academy/ the guide is interesting, haven't explored the gamehttp://explainshell.com/ type in a command & options & it will give an explanation
https://www.learnenough.com/command-line-tutorial learn enough bash to be dangerous
http://cs.gettysburg.edu/~tneller/dept/bash-tutorial.html (where you see yypasswd use passwd instead)
http://www.linuxcommand.org/ really clear overview but uses html
Scripting with bash
http://learnshell.org an interactive website for scirptingtldp.org's Advanced Bash-scripting guide
Steve Parker's Bash shell scripting tutorial
Linux General (system and network administration)
http://www.linux-books.us/ free linux bookshttp://www.linux-books.us/gnoppix_0001.php rute users guide
See alsohttp://wiki.pcampbell.profweb.ca/index.php/Bash