ActiveState - ActiveState offers a PaaS-based infrastructure that enables developers to build and deploy apps to the cloud.
UptimeRobot - Free Website Uptime Monitoring
Nitrous - Nitrous is a web-based development platform that allows developers to collaborate on their projects in real-time, deploy to production servers with one-click, and to snapshot their projects quickly and easily.
AppBeat - AppBeat is reliable website monitoring service that alerts you when there is a downtime or failure. It also measures performance and provides functional tests.
Bannerboo.com - Bannerboo is the world's easiest online banner maker.
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.