Amazon

Full review
I love amazon.com. I have bought thousands of dollars worth of stuff from them and keep coming back. What I appreciate the most are
1. Ease of checking out2. Variety of choices available for most categories3. Prices4. Return policy5. Free shipping for most items when you spend $25 or more - I am pretty sure that they're the reason that so many online sellers now have similar policies6. Ease of tracking items - both shipped and previously-ordered items7. Ability to share wish lists if you want - my nieces update their amazon.com wish lists on a regular basis and I just order presents from their lists for birthdays, Christmas, etc.8. You can buy items from Amazon.com and get the free shipping described in item 5, or you can buy items from their marketplace that are used or new but sometimes cheaper than Amazon.com sells them9. Amazon.com shows ratings for their items as well as for their vendors in the Amazon.com marketplace
Regarding item 4, I've returned a few items of the hundreds I have bought from there and they have never disappointed me. I just returned some baby shoes that were too small and they made things easy, just as they had done for other items I have returned.