Glui - glui - GLUI is a GLUT-based C++ user interface library which provides controls such as buttons, checkboxes, radio buttons, and spinners to OpenGL applications. It is window-system independent, using GLUT or FreeGLUT.
Muzli - UI/UX and Design Inspiration Chrome Extension
Red Pen - Red Pen lets you upload your design, share a short URL, and get live, annotated feedback super-fast.
DesignMunk - Landing Page Inspirations
GoodUI Fastforward - Lift your conversion rate with repeatedly AB tested patterns
UI Movement - The best UI design inspiration, daily