Since Ebay Guides doesn't allow people to put links to non-Ebay sites, I put the link for Ebates (where you can find the coupon) on my Ebay Profile Page: Click here to find the Ebay Coupon link provided by Ebates (it is to the right of the empire state building photo, simply cut and paste it into your browser)
Since this is a guide, I will go over some of the info I learned since I started using Ebates. From my research, I found that Ebay has recently hired Ebates to promote sales. Every time you win an Ebay auction, you get refunded up to 5% of what you paid for the auction. You can even use this on top of Ebay Bucks. 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 commission (which is how they give you the discount). 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), JC Penney (8% off), Neiman Marcus (8% off), Nordstrom (5% off), DSW (4% off), Macy's (6% off), Sears (5% off), K Mart (6% off), Home Depot (3% off), Walmart (1% off), Target (2% off), Travelocity (5% off), Orbitz (5% off), Staples (6% off), Best Buy (1.5% off) etc. Note that these percentages, including that for Ebay, often change, 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 restrictions are 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. Cash back for your future Ebay purchases adds up fast (as I've been finding out). Everyone should be doing this now that the Bing 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 :)
I put the link for Ebates on My Ebay Page (Ebay doesn't let you include direct links in Guides): My Ebay Page for the Link to Ebates
Hope you find this as helpful as I did.