Huh, I totally forgot about Pivotal Tracker. There was a phase where every project I was on used it.

The killer feature was the UI. When the alternative was basically JIRA, Pivotal was so quick and easy to use. That front page view that let you see every task in a compact list, and easily drag things around to reprioritise was pretty revolutionary.

Now it seems kind of passé but it really was pretty excellent at the time.