Some time ago, reading this entry I found a nice image and a pointer to a better book entitled "Thinking Forth". To my surprise, the LaTeX sources of the book were ready to download, with pearls like:

%% There's no bold typewriter in Computer Modern.
%% Emulate with printing several times, slightly moving

\newdimen\poormove
\poormove0.0666pt
\newcommand{\poorbf}[1]{%
\llap{\hbox to \poormove{#1\hss}}%
\raise\poormove\rlap{#1\hss}%
\lower\poormove\rlap{#1\hss}%
\rlap{\hbox to \poormove{\hss}\hbox{#1}}%
#1}

%\let\poorbf=\textbf
\renewcommand{\poorbf}[1]{{\fontencoding{OT1}\fontfamily{cmtt}\fontseries{b}\selectfont#1}}

in which it can simulate the bold stroking of a font that doesn't have it. Since reading that, I was unaware of \llap and such, but now I can use them to define boxes, etc.

So, my question is twofold:

1. Do you know of sites that show that relatively advanced use of TeX/LaTeX in terms of useful recipes, and
2. Do you know any books that offer their TeX/LaTeX source to inspect and learn (and that are worth doing so.)?