Zabbix - Track, record, alert and visualize performance and availability of IT resources
Next Step for Trello - Check tasks directly from your Trello boards
Statista - The Statistics Portal for Market Data, Market Research and Market Studies
Fero - Super-easy user flow analytics & integrations for creators
Montecarlito - MonteCarlito is a free Excel-add-in to do Monte-Carlo-simulations.
Scrum Study Cards - An easy to understand overview of the Scrum framework.