The very compact revserse HTTP & HTTPS proxy "pound" (
http://www.apsis.ch/pound/ ) provides the load balancing you are
probably looking for, among other nice features such as application
tracking, URL sanitizer, server test/fail-over/-back, and application
session tracking.

I am currently running it on an OpenBSD3.9-current server which is
located in one of my firewall's DMZs. Actually, I consider
implementing a pound as a m0n0wall extension module, as it is small
and would make a great funtional extension for m0n0wall without adding
much bloat (security exposure, code size, parametrization complexity,
etc.).

However, before getting started and seting up a m0n0wall development
environment (again), I somehow wait for clarification on what will be
m0n0wall's next OS platform :-)

Rolf