Invision - Prototyping and collaboration for design teams
ProjectHuddle - Get design feedback and client approval using WordPress.
Dotarchy - Pick a topic, discuss it, make some Friends
Start on Android by Google - Developer program to optimize your app before you launch
Savahapp - The all-in-one design sharing, collaboration, workflow and app prototyping platform
zipBoard - ZipBoard is a web-based visual bug tracking & issue tracking tool that helps developers, testers and project managers collaborate during website and elearning development.