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.
Kafka - Apache Kafka is publish-subscribe messaging rethought as a distributed commit log.
Serilog - Backend Development and Utilities
Snare - Snare is well known historically as a leader in the event log space.
Logmatic - Logmatic is a log centralization, analytics & visualization platform to improve software & business performance.