Despite Amazon's ridiculous patent activities I still like their website a whole lot. I agree with wickline, and like to use them for discovery but not purchase. My one weakness are the used books. I do buy those from time to time, and justify it in my mind because I'm helping support little used bookstores around the country.
A while back brian d foy turned me onto using Amazon's Web Services. I wrote a program to periodically suck down my wishlist and and store it on my stripped down website run by Rael Dornfest's blosxom.
Today I woke up at 3AM and couldn't fall back to sleep, and started poking around at the wishlist program to notify me when there is a used copy of the book available which falls below a certain (configurable) percentage of the list price. Now I will get email updates whenever some books I want are available for cheap from one of the used book stores. I'm sure Amazon gets a cut of this however.