Super simple web proxy

Hello all.

I currently have a couple of simple semi-official intranet sites running
on a computer at work (I shanghai’d it to run these sites along with
it’s primary purpose). Each site is running on one mongrel server that
hosts the ruby/rails app. One is running on port 80 and the other is
running on port 81.

What I am after is a super simple WINDOWS compatible program sitting on
port 80 that will do HTTP proxying and forward the request to one of the
mongrel servers (Running on ports 3000 and 3001 respectively) depending
on the URL. (The friendly IT admin is happy to point a few DNS records
to the server)

I don’t want to install something heavyweight like Apache with mod_proxy
and Lighty is right out of the picture with cygwin. I need something
small and lightweight that would preferably use sweet FA system

I have looked at the various pen/pound mongrel cluster programs but
those are for spreading one site out over many machines.

If anyone has any suggestions they would be much appreciated