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.

The Product Management guide - A book on how to create and ship products that people love

Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.

Intercom on Product Management - The ultimate resource for aspiring product managers

Basecamp - A simple and elegant project management system.

Xobin - Most Comprehesive Pre-Employment skills testing and Psychometric Assessment Platform.