Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Mockupea - Mockupea is an online tool for creating 3d book mockups with a lot of features.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Stackoverflow '90s - Bring back '90s to Stackoverflow with this extension
Better Uptime - We call you when your website goes down
Box Shadow Generator - Generating CSS3 multilayer box-shadow has never been easier.