I found this on dealcatcher.com.

If you go to www.live.com and enter something to search for, when your search comes back, click on the ebay link. They are offering 30% back, up to $200. You have to use paypal and have a microsoft cashback account and Buy It Now on ebay, I think anyway. Once you click on the Buy It Now link, it will tell you if the item is not included in the promotion before you actually make a commitment to purchase. I've been looking at Nikon D80 cameras and lenses on there with this promotion. You can use it more than once, but you have to go back to the beginning and search for each item and purchase them separately. So I've been comparing buying the camera body and lenses separately, since I wouldn't get the full 30% back on a bundle with a couple of lenses.

Here is the link to the fine print/details. You can also link through to this at dealcatcher.com. On dealcatcher, many people were using the discount to buy tires. It doesn't look like it is only available today.