Everyone agrees Costco is a fabulous store in many ways. Most also agree that shopping at Costco can be an unpleasant experience for several reasons. Not everything from the store is available online from Costco.com, but much is, and it worthwhile checking before schlepping to the store, especially if you're looking for just an item (say walnuts, which are difficult to locate int the store anyhow) or two. In the main, shipping is free.
Link to Costco.com