log4net - log4net is a tool to help the programmer output log statements to a variety of output targets.
logstash - logstash is a tool for managing events and logs.
AWS CloudTrail - AWS CloudTrail is a web service that records AWS API calls for your account and delivers log files to you.
rsyslog - Rsyslog is an enhanced syslogd supporting, among others, MySQL, PostgreSQL, failover log...
Logary - Professional logging metrics and analytics for your apps
Graylog - Graylog is an open source log management platform for collecting, indexing, and analyzing both structured and unstructured data.