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.
Walling for Windows - Visual walls for your ideas and projects. Now on Windows.
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.
Microsoft Whiteboard - The canvas where ideas, content, & people come together.
Infinity - Infinity is a fully flexible work management platform where you can organize all your work, your way.
Milanote - Milanote is a note taking app for creative work.