I shop Walmart locally, and when I am looking for very specific products, I will check their website first. You can often buy online and pickup in store same day. Another advantage to their website is their pricing. You can often find the products cheaper online (vs the store), purchase them, and pickup same day. Money saving!
I love how affordable they are in comparison to other sites. I had no problems with my order, and the items were shipped promptly. I would highly recommend.
I love using Groupon. It's very beneficial around the holidays when I am shopping for multiple people. They have discount specials from time to time as well, which makes purchasing groupons even more cost-effective.
Amazon is such a great resource when you are looking for multiple products. I always shop and compare for just about every product that I purchase online, and they are almost always the site with the most discounted products.