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.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Better Uptime - We call you when your website goes down
Bigtent - BigTent is a web-based organization and communication portal for groups.