First up is Amazon.com. Amazon runs some killer deals during the holiday season, and I can always find some of the best deals for my friends' presents. Especially in the days leading up to Christmas, Amazon is a perfect place to shop. They're also currently running a 12 Days Of Deals sale, so be sure to check in on that!
Another favorite online shopping destination of mine is Etsy.com. Etsy is an online marketplace where small, independent owners sell their products. They will have nearly anything you can think of, and these shop owners will cut some amazing deals this time of year. It's also great if you're buying the same thing for several people because, if you contact the owner, they'll often give you a deal on items if you're buying several at a time! There's no harm in trying, and it often pays off!