AbTest.io - A free url shortener with A/B testing features
Optimizely - A/B testing you'll actually use.
GoodUI Evidence - People's A/B test results that show which UI ideas work best
VWO - Use VWO to tweak, optimize & personalize your website with minimal IT help.
PreFlight - Preflight is an Automated Web Testing tool. Allows everyone to automate Web UI tests.
Chartbeat - Chartbeat shows you real-time traffic to your website and allows you to set alerts for any downtime or spikes in traffic.