What are the best Agile Project Management Tools?

Taiga.io, Sprint.ly, Sketchboard for Slack, Acunote, and LeanKit are the most popular tools in the category "Agile Project Management". "Free. open source. agile project management" is the primary reason developers pick Taiga.io over its competitors, while "Great Kanban based agile project management software" is the reason why Sprint.ly was chosen.