WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Optimizely - A/B testing you'll actually use.
Oh Dear! - Website monitoring, without the hassle
108 Proven Split Test Winners - Simple tweaks to make to your website, to make more money!
Freshworks - Delight your customers, from wherever you are
Growth Book - The Open Source A/B Testing Platform