ConTeXt Sources (MkII)
Apart from the manuals, the source files (especially, some of the old ones) contain excellent documentation and examples. If you want a pretty printed pdf of a source file, say core-rul.tex, you can type
texmfstart texexec --module kpse:core-rul.tex
But this apparently doesn’t work any more (i.e., I simply entered that line in the Mac terminal and nothing happened). Am I doing something wrong?