On the marketing team at Kong, we use Trello for tracking our tasks. Other teams use JIRA but we don't need to do any storypoint estimation and don't really operate in sprints, so we find it to be a bit of overkill. Trello has easy-to-configure integrations with most of the tools we use, and a great mobile app which makes it easy to add things to to-do lists even when we aren't in front of our computers. If there's one thing I would add to Trello it would be some kind of time tracking to help us stay focused and to be able to look back on tasks and see how long each one took. It would also be nice if there were an epic equivalent so that we could group cards into projects, but this can sort of be hacked around using lables. Over all we're pretty happy with Trello! Would recommend!