From my research, I found that Ebay has recently hired Ebates to promote sales during the recession. Every time you win an Ebay auction, you get refunded 5% of what you paid for the auction. You can even use this on top of Ebay Bucks (for a total of 7% off). The way this works is that Ebay pays Ebates a commission each time someone uses Ebates to buy something on Ebay. In turn, Ebates pays you part of that comission (which is how they give you the 5%). This way, everyone makes out (including Ebay). Ebates has also negotiated similar coupons with over 1600 popular online stores Examples of other coupons include Amazon (3% off), 1 800 Flowers (10% off), ProFlowers (16% off), FDT (20% off), TurboTax (7.5% off), Kohl's (6% off), Sears (5% off) , JC Penney (8% off), Drugstore.com (6% off), Neiman Marcus (8% off), Nordstrom (5% off), DSW (4% off), Macy's (6% off), Sears (5% off), K Mart (6% off), Overstock.com (2.5% off), Home Depot (3% off), Walmart (1% off), Target (2% off), Half.com (4% off), Travelocity (5% off), Orbits (5% off), Staples (6% off), Best Buy (1.5% off) etc. Note that these percentages often changes, so they may be higher or lower depending on what the current offer is.
Again, these coupons can be used an unlimited amount of times (making this better than a typical coupon code you get in the mail). With respect to Ebay, the only restrictions is that this doesn't work for charity auctions or for the "Ebay Gift Card" category. Otherwise, you can use this for all other types of categories and with any type of auction style format (ie Buy It Now, Best Offer, Auction format etc).
I hope this spreads the word. 5% off all future Ebay Purchases adds up fast (as I've been finding out). Everyone should be doing this now that the Bing.com reward program is no longer available and because Ebay fees are starting to get really high for sellers (however, these high Ebay fees are what fund this program...so we can't complain too much :) Bingcrumbs.