I have been testing several different open source shopping cart management tools. The one I am currently messing around with is called Zen Cart.
The basic green template that Zen Cart comes with is pretty bland so I decided to find a snazzier one. I was originally looking on the Zen Cart site under the template downloads section, reading about the design, and then downloading and installing on my server to test it to see if I liked it (some themes had demo sites, but about half didn't). My original method was ok, but very time consuming.
Today I happened to stumbled upon a much better way to test templates: zencarttemplates.info
"Test drive free Zen Cart templates.
Choose your favorite. Download it!
Now you can see all the free templates available from the Zen Cart Support forum in action, compare them side-by-side and download the one that best suits your needs. Just follow this easy process."