ProjectHuddle - Get design feedback and client approval using WordPress.
Usersnap - Visual Feedback - Usersnap helps your business with its versatile feedback platform to build better, more successful products and services with the help of user feedback. Collect feedback along your product development lifecycle. Try it for free.
Savahapp - The all-in-one design sharing, collaboration, workflow and app prototyping platform
Feedback by Pixelic - Painless design feedback and version control.
Specfox - A free platform for creating beautiful website and mobile app specification documents for your team. No more word templates!
Sesov - A community for anonymous design feedback