California guys have developed an interesting service Pixelapse, which allows you to upload graphic files to the site (integration with Photoshop), automatically creates versions of files and provides rich possibilities for discussing work.
One word Pixelapse is GitHub for designers.
Briefly about the possibilities:
Comparison of two or more versions, by placing them next to each other or by the overlay method. Cool stuff, a kind of graphical merge in the browser, fast and convenient.
In the comments, you can refer to specific versions and to users using username and [ref #]. Revisions (file versions) are inserted into the comments feed in the form of thumbnails.
A cool opportunity to highlight a region in the image and comment on it.
Pixelapse supports Photoshop, Illustrator and Fireworks!
The project at the testing stage, you can leave an email and send an invitation. www.pixelapse.com - site address www.pixelapse.com/hn - demo page where you can explore the capabilities of the system ')
When creating a service using Bootstrap - it came out very stylish. The site design deserves respect, I really liked the design of the profile in the form of a badge.
UPDATE DenimTornado in his comment suggests that at the current time without the Mac'a service will not be able to use.