Slickdeals is one of my favorite apps and websites. There is lots of info on anything that there is to buy. You can go directly to the website here . Download the app on the ios here, android here.
Buyvia is a newer app and website that works the same as slickdeals. You can download their android app here or for ios here. Their website is not as user friendly as slickdeals but works the same.
Also if you are looking for things to purchase online don’t forget that many retailers are offering free shipping and always amazon.com has prime or other free shipping deals on certain products. Here is a comprehensive list of those retailers: Black Friday 2015: Target, Best Buy, Apple and others offering free shipping.