Optimizely - A/B testing you'll actually use.
Startup Toolkit - Interactive how-to guides to launch your startup
SplitMetrics - SplitMetrics is the A/B testing platform for App Store and Google Play page to discover the most converting icons, screenshots, video, etc.
Manager checklist - Cheatsheet of things every manager should do
Chartbeat - Chartbeat shows you real-time traffic to your website and allows you to set alerts for any downtime or spikes in traffic.
Where To Post Your Product - A curated collection of 280+ websites to share your startup