Rainer Schöpf's verbatim.sty provides a comment environment which
excludes everything between \begin{comment} and \end{comment}.
This package is available as part of macros/latex/packages/tools
A more general environment for doing the job is Victor Eijkhout's comment.sty, which lets you define environments for inclusion or exclusion in a document, thus offering a primitive configuration structure. It is available from the CTAN sites in macros/latex209/contrib/misc/comment.sty