I use Evernote a lot to collaborate with my web design teams & fellow photographers. And I also use Evernote to keep my data shared with my numerous Mac devices like laptop, iPhone and iMac. Now I also use Skitch along with Evernote to collaborate and share marked up photos with my teams.
Skitch is a free photo software that helps you communicate visually with friends, co-workers, and your teams. You can annotate images with arrows, shapes, and text & share with your groups to collaborate on projects and seek opinions on your projects.