slem – Slanted emphasis in LaTeX 2.09
A jiffy package to cause \em in LaTeX 2.09 to use \sl in place of the standard \it. Note that the package will not work in LaTeX 2e.
Maybe you are interested in the following packages as well.
isf: Access italic computer modern sans in LaTeX 2.09
settosize-ltx: Scale text to make it fit a given width
maybemath: Make math bold or italic according to context
slemph: Slanted emphasis in LaTeX