comment-pln – Comment macros for use in Plain TeX
Defines macros \comment and \endcomment such that everything between the two is ignored.
Maybe you are interested in the following packages as well.
- versions: Optionally omit pieces of text
- ifthenx: Extra tests for \ifthenelse
- ifthen: Conditional commands in LaTeX documents
- draftfigure: Replace figures with a white box and additional features