StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Workona - A better way to work in the browser.
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.
OneTab - Whenever you find yourself with too many tabs, click the OneTab icon to convert all of your tabs into a list. When you need to access the tabs again, you can either restore them individually or all at once.
UptimeRobot - Free Website Uptime Monitoring
Session Buddy - Manage Your Browser Sessions