I've posted several times about my search for the perfect flooring for my screened-porch/sunroom. It had horrible, smelly carpet that I tore up to expose ugly concrete. I though about painting, staining, tiling, but I finally found the perfect solution. It is a modular wood decking product called Platta from Ikea. It cost less than $4/square foot and my 86 year old father and I laid 150 square feet in less than 2 hours. It looks terrific and is very comfortable to walk on. I am not sure how it would work outside--it might not due well in snow and rain, but in my porch, it should do fine.
Disclaimer--I do not work for Ikea but I do shop there a lot.