UI Coach - Become a better UI designer in 30 days
ProjectHuddle - Get design feedback and client approval using WordPress.
Evrybo - Free design collaboration and prototyping tool
Invision - Prototyping and collaboration for design teams
Savahapp - The all-in-one design sharing, collaboration, workflow and app prototyping platform
Shotgun - Production tracking, asset management, and review. Helping your whole team go faster.