I've been an avid user of Trello. Easy to use, very simple for any external stake holders to get into (and nice permissions) while being super simple to use. Th

I've been an avid user of Trello. Easy to use, very simple for any external stake holders to get into (and nice permissions) while being super simple to use. They've got a great amount of 'example' boards as well: https://trello.com/inspiringboards https://trello.com/inspiringboards