Red Pen - Red Pen lets you upload your design, share a short URL, and get live, annotated feedback super-fast.
DesignMunk - Landing Page Inspirations
Invision - Prototyping and collaboration for design teams
Muzli - UI/UX and Design Inspiration Chrome Extension
FLTDSGN - Daily showcase of the best flat UI design websites and apps
UI Movement - The best UI design inspiration, daily