I have a question about finishing outdoor furniture. I'm planning to build
a
sofa, chair and coffee table out of either teak or Honduran mahogany (if
someone has another good suggestion, I'm open.) I don't want the wood to
weather to grey but rather maintain the natural color of the wood. I
realize
yearly maintenance will be required. I was thinking exterior grade
polyurethane. Can anyone give me some suggestions as to how to proceed?

Try Sikkens Cetol. It's the best product that I've come across. The finish
will last a few years, and when it's time to re-apply it can go over top of
the old finish - no stripping required.