You can actually play with cell phone interfaces before buying at TryPhone. If you're like me, just spending a few minutes in the store playing with a cell phone isn't enough time to see how all of the features work -- TryPhone puts up interactive images on their site of cell phones and their operating systems so that you can play around with features. The number of phones currently listed is pretty slim, but they promise to be adding more phones shortly.
The site is also social, allowing users to post reviews and their experiences with the phones listed. Quite frankly, I could see the features in this site being very useful as an add-in to Amazon or even a carrier sales site.