Lean Analytics - A/B testing React apps made easy
Decidr - Make better decisions with quick A/B polls
SEOTesting.com - Easily track the changes you make to pages and websites, to see if they have an effect on Google rankings and clicks.
Go Fucking Do It - Set a deadline and a price. If you fail, you pay.
AbTest.io - A free url shortener with A/B testing features
Keyword Explorer by Moz - Find the best keywords to improve your website's SEO traffic