Did you know you could buy a gift card online for LESS than the value that's left on the card? Some places tack on shipping costs, which could result in you actually paying MORE than the value. So not all gift card websites are created equal. Let's explore your options...
Gift Card Granny
I give Gift Card Granny the #1 spot in my ranking because they provide the best of both worlds. If you want a new gift card and don't mind paying full price, they have you covered. If you want a discount gift card that has an odd value, but which you can purchase for below the value left on the card, they compare which gift card websites (including the others in this review) have the best deal. So you can compare many of the sites below all from this one location. They'll also tell you how much some of the sites below are buying cards for, and will link to to the one that's offering the best price if you happen to be selling a gift card for cash. So you can buy new, buy discounted, or sell all from one place and be sure you're getting the best deal possible since everything is compared right there on www.giftcardgranny.com
In terms of places that buy and sell gift cards (as opposed to Gift Card Granny, which is more of a comparison shopping site) I prefer Plastic Jungle. You can save up to 30% on discounted gift cards here, but generally you'll find the discount to be around 4% - 5% on the big-names like Best Buy and Macy's. Plastic Jungle is competitively priced, although Card Pool does often get the better of them. I find PJ to be a little easier to use, and I trust them. See www.plasticjungle.com for more.
I'm not sure what I'm supposed to do on this site at first. There' s not search function, and I had to click around for a few minutes before I found where I could see what gift cards were for sale. Then I had to scroll down a long list to find the one I was interested in. Here's a company that seems to be relying on having the best domain-name instead of the best site.
Gift Card Castle
GiftCardCastle often has some pretty good discounts (sometimes a percent or two above the rest), but I find their site difficult to navigate at first (not as bad as Gift Cards .com though) and it doesn't inspire trust like the above three sites do. I like very much that they call out "Free shipping and no tax" so you know that the price you see is the price you pay. Once you figure out how to navigate the site it becomes very easy to use.