There’s a wealth of excellent collaboration tools to make it easier to get feedback and approve artwork in a timely, professional manner. For freelancers or small agencies on a tight budget, these free tools can make sharing design concepts in real time a breeze, without breaking the bank. via 14 Fantastic Free Tools for Design Collaboration | Mashable

The 14 tools reviewed are:

1. Red Pen
2. Bounce
3. Flatsies
4. Prevue
5. Marqueed
6. GoVisually
7. Invision App
8. Design Drop
9. Framebench
10. Concept Inbox
11. Skwibl
12. EasyProof
13. Apollo
14. Redmark