Anent USB and parallel interfaces, take a look at
http://www-user.tu-
chemnitz.de/~heha/bastelecke/Rund%20um%20den%20PC/USB2LPT/ul-
15.htm.en
Provides full virtualization of all parallel port lines. Click on
the link for V1.6, and the crystal goes away. Cheap to build and
very small with open source.
--Chuck