The emTeX distribution (see TeX systems) contains a driver for the LaserJet, dvihplj.
Version 2.10 of the Beebe drivers supports the LaserJet. These drivers will compile under Unix, VMS, and on the Atari ST and DEC-20s.
For Unix systems, Karl Berry's dviljk uses the same path-searching library as web2c. dviljk is no longer distributed as a separate source, but the teTeX distribution holds a copy under the name dvilj.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=HPdrivers