Prometheus - An open-source systems monitoring and alerting toolkit.
BOINC - BOINC is an open-source software platform for computing using volunteered resources
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Apache Mesos - Apache Mesos abstracts resources away from machines, enabling fault-tolerant and elastic distributed systems to easily be built and run effectively.
StatsD - Simple daemon for easy stats aggregation.
JPPF - The open source grid computing solution.