Invision - Prototyping and collaboration for design teams
Pastel - Sticky note-based feedback collection tool for live websites
Red Pen - Red Pen lets you upload your design, share a short URL, and get live, annotated feedback super-fast.
MarkUp - Collect feedback on digital projects right in the browser.
BugHerd - BugHerd: The Website Feedback Tool for Agencies
Viewflux - Feedback, prototyping and collaboration for designers