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.
log4net - log4net is a tool to help the programmer output log statements to a variety of output targets.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Serilog - Backend Development and Utilities
Better Uptime - We call you when your website goes down
Logmatic - Logmatic is a log centralization, analytics & visualization platform to improve software & business performance.