List of LaTeX macros for writing packages

 Martin Scharrer has compiled a list of LaTeX macros useful for people that are building packages. This is a great document, I personally have spent numerous times source-diving into the base LaTeX file /usr/share/texmf/tex/latex/base/latex.ltx to find how things work, scratching my head very hard to understand what macros like \@dblarg do. This is even more difficult than it seems as macros tend to be used at the end of other macros, i.e., without their arguments.

More information at:
http://www.scharrer-online.de/wiki/LaTeX/Docs/macros2e