ProjectHuddle - Get design feedback and client approval using WordPress.
Invision - Prototyping and collaboration for design teams
Savahapp - The all-in-one design sharing, collaboration, workflow and app prototyping platform
Red Pen - Red Pen lets you upload your design, share a short URL, and get live, annotated feedback super-fast.
Specfox - A free platform for creating beautiful website and mobile app specification documents for your team. No more word templates!
Pastel - Sticky note-based feedback collection tool for live websites