Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Octoview - The missing preview feature for GitHub
GoodGantt - The best Gantt chart for Trello®
Dyllo - A clean and simple way to view a Github user's information
Paws for Trello - The best way to use Trello on your desktop