Buying coupons online is a great way to save money. Ebay is a great place to purchase coupons that you use frequently. Thanks to Wicked Cool Deals for this great article on buying grocery coupons online.
I would also like to add that while you are looking for coupons on E-Bay, don't forget to also look for other than grocery coupons (clothing, coffee, homegoods.)
I frequently purchase Kohls coupons on E-bay from a reputable seller. (I recently bought 20 for $2) These $5 off a $5 purchase result in me getting some great items for free. The key is to shop the clearance section with these coupons and since you can only use one coupon at a time, check out when your items total the $5 minimum. Then just go back and buy again. It takes a little extra time, but for the free shirts, I've gotten my daughter, she is very appreciative, and it's worth the effort.
Another good coupon to purchase on E-Bay is 10% off Lowes. These coupons can save you up to $500 each. If you prefer to shop at Home Depot, just take the coupon there and they'll honor it.
Watch for Victoria's Secret coupons, NY&Co, as well as, Lane Bryant. all good stores that offer great savings coupons.
E-Bay is a great marketplace for coupons of all kinds, and gift certificates too. So get out there, place a bid, and Save.