RadioShack has a good selection of basic antenna mounting kits and mast to attach antennas to your roof, chimney, eves, vent pipes, or walls.
Here are some links to some tree mast mounts:
The Do-It-Yourself Chimney Mast page has a new home.
-- Darik Horn
My Googling for Universal mount brought me to this Pacific Wireless page and a few others. PW was the cheapest, I couldn't find anything at the RatShack site. http://www.rangeextender.com/accessories.html --Jim Sutton