elmah.io - The coolest cloud based error management system for .NET web applications. Based on the de-facto standard error component ELMAH, logging errors from your webserver have never been this easy. Full-text search, notifications, API and much more.

Serilog - Backend Development and Utilities

Raygun - Raygun gives developers meaningful insights into problems affecting their applications. Discover issues - Understand the problem - Fix things faster.

log4net - log4net is a tool to help the programmer output log statements to a variety of output targets.

Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.

Logmatic - Logmatic is a log centralization, analytics & visualization platform to improve software & business performance.