Many of David Carlisle's more substantial packages stand on
their own, or as part of the LaTeX latex-tools set; this set
contains: Making dotless 'j' characters for fonts that don't
have them; A method for combining the capabilities of longtable
and tabularx; An environment for including Plain TeX in LaTeX
documents; A jiffy to remove counters from other counters'
reset lists (now obsolete as it has been incorporated into the
LaTeX format); A jiffy to create 'slashed' characters for
physicists.