GitHub Reader - A quick way to browse GitHub issues and pull requests.
Zube - Project management for developers.
Shrink for Github - A macOS app for your Github issues
ZenHub - ZenHub is how the world's best software teams work together. Trusted by NASA, Docker, and Rackspace. Start free today!
Codetree - You can manage your entire development process through GitHub.
Nifty - Manage projects, work, and communications in one place.