Synfig Studio - Just another WordPress site
Invision - Prototyping and collaboration for design teams
Duik - Comprehensive animation and rigging toolset for Adobe After Effects
Proto.io - Create fully-interactive high-fidelity prototypes in minutes that look and work exactly like your app should. Sign up for a free 15-day trial and get started.
Limber for After Effects - IK system for After Effects using shape layers as limbs for character animation
Zeplin - Collaboration app for UI designers & frontend developers