Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
Webvizio - This free website feedback tool & website review software allows managers and teams to collaborate on website revisions in real time. Join for free now!
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Collaboration from CloudApp - Collaborate with commenting, annotations, and faster sharing
Balloon - A drop box for your Dropbox
Collaboration by Instapage - Landing page design collaboration for marketing teams