www.marthastewart.com has a tutorial on how to paint a door mat. We visited my brother in his new house today and did a version of this project as a house warming gift. The rug was simple and cheap ($6 at the local hardware store). All I needed to do was add his house number.
In Microsoft Word I printed the numbers in size # 675 and font Edwardian Script ITC BOLD.
I cut out the letters for a stencil (the '6' was tricky with the middle removable.)
Then I dabbed brown acrylic paint mixed with fabric medium in the stencil. Voila!