It lets you keep a list of games you want to buy, showing you all the legitimate stores and the best prices, lets you set up notifications based on different parameters, lets you import your Steam wishlist, shows what sites have bundles, coupons, giveaways, etc. I check it for every game I want and have saved hundreds.
Plenty of people know of it, but more people should: isthereanydeal.com
It lets you keep a list of games you want to buy, showing you all the legitimate stores and the best prices, lets you set up notifications based on different parameters, lets you import your Steam wishlist, shows what sites have bundles, coupons, giveaways, etc. I check it for every game I want and have saved hundreds.