AbTest.io - A free url shortener with A/B testing features
Optimizely - A/B testing you'll actually use.
Marpipe - Automate Your Ad Testing, Optimize Your Creative
Google Analytics - Improve your website to increase conversions, improve the user experience, and make more money using Google Analytics. Measure, understand and quantify engagement on your site with customized and in-depth reports.
StoreMaven - A/B testing and design platform for App Store and Google Play icons, screenshots and videos.
VWO - Use VWO to tweak, optimize & personalize your website with minimal IT help.