A little over a year ago, I did a whole bunch of online shopping, including quite a bit at
amazon.com, and I learned a couple of things. One is there are at least a couple of sites that list tons of online discounts. However, I only remember one particular name:
www.slickdeals.net. I haven't checked to see if they are still in business.
I did find a few other avenues to be more useful: credit card sites. For example, discover.com, americanexpress.com, mastercard.com, etc. They typically list their "online partners" and you can usually find free shipping and stuff like that. I also vaguely remember that the NYTimes site also had online partners.
In other words, it may take some digging, but lots of online shopping sites have discounts listed somewhere or other.
Good luck!