Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
Basil Chat - Design feedback via chat
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.
Planogy - A feedback platform for all the creative work
Drag Team - The simplest way to share emails as a team.
Feedback by Pixelic - Painless design feedback and version control.