They ship from several locations including drop ships from suppliers so your order may involve several packages delivered at different dates. Generally their shipping is very quick too, sometimes two days after an order.
I always bundle my purchases to get to the free shipping threshold ($50).
I use Wal-Mart stores regularly, but not their website. Most of my Amazon shopping is used books, but Amazon also offers a much broader selection of items. WalMart.com is poorly organized and awkward to use.