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.
Codegiant - Codegiant - Issue tracking, git repositories, continuous integration and documentation in a single platform.
Planyway - Visual project management for Jira and Trello: manage resources, build project roadmaps, use time tracking.
Scrumpy - A simple, beautiful and agile project management software
Wiplo - The easiest way to organize and run your business workflows.
Nifty - Manage projects, work, and communications in one place.