nxlog - NXLog offers log management solutions for companies of all sizes.
logstash - logstash is a tool for managing events and logs.
Nagios Log Server - Nagios Log Server is centralized log management, monitoring & analysis software. Quickly & easily manage, monitor and analyze log data. Download Today!
Graylog - Graylog is an open source log management platform for collecting, indexing, and analyzing both structured and unstructured data.
Splunk - Splunk's operational intelligence platform helps unearth intelligent insights from machine data.
Sentry - Open-source error tracking that helps developers monitor and fix crashes in real time. Iterate continuously. Boost workflow efficiency. Improve user experience.