itch.io - An online game marketplace and community.
HyperSpin - HyperSpin is an animated arcade frontend for Windows for use on Home Arcade Machines.
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
LaunchBox - LaunchBox is a portable, box-art-based games database and launcher for DOSBox, emulators, arcade cabinets, and PC Games. Download it free!
Ubisoft Club - Ubisoft Club app enables you to get updates about your favorite games timely.
OfflineList - A widely-used, multi-platform ROM manager.