Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
DomainWatch - Domain Monitoring Made Easy
UptimeRobot - Free Website Uptime Monitoring
Domainz.io - Premium domains, for not so premium prices
Simple Ops - Simplify website performance and uptime monitoring with alerting, ssl check, chrome ux metrics, multi locations
dofo.com - Domain search platform Dofo.com gathers all registered (350 million) domains of the world in a single place. Dofo also brings together all the domain names that are on sale, provides useful features, all completely free.