http://www.joshstaiger.org/archives/2005/07/bash_profile_vs.html

[ Safe mode ]
http://redsymbol.net/articles/unofficial-bash-strict-mode/

http://bytemuse.com/post/the-terminal-crash-course-and-reference-sheet/

bash usefulness
http://www.fizerkhan.com/blog/posts/What-I-learned-from-other-s-shell-scripts.html

[ robust scripts ]
http://www.davidpashley.com/articles/writing-robust-shell-scripts/

http://www.shellcheck.net/#

[ Shell scripting guide from google ]
http://google-styleguide.googlecode.com/svn/trunk/shell.xml#Indentation

links to resources to learn UNIX tools https://news.ycombinator.com/item?id=2415365

bash mistakes http://www.pixelbeat.org/programming/shell_script_mistakes.html

less common commans
http://www.danielmiessler.com/blog/collection-of-less-commonly-used-unix-commands

http://www.webdesignporto.com/get-started-with-unix-command-line-vim-and-sh-for-the-total-windows-newbie/

http://www.kfirlavi.com/blog/2012/11/14/defensive-bash-programming/