AbTest.io - A free url shortener with A/B testing features
Invision - Prototyping and collaboration for design teams
GoodUI Evidence - People's A/B test results that show which UI ideas work best
Red Pen - Red Pen lets you upload your design, share a short URL, and get live, annotated feedback super-fast.
PreFlight - Preflight is an Automated Web Testing tool. Allows everyone to automate Web UI tests.
Pastel - Sticky note-based feedback collection tool for live websites