Traq - Traq is a PHP powered project manager and issue tracker featuring multiple projects, milestones...
Zabbix - Track, record, alert and visualize performance and availability of IT resources
16bugs - 16bugs is an all-in-one bug tracking software that makes it easier for you to manage all sorts of bugs in performance with the simple interface; ultimately, you will be more productive for sure.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Trac - Trac is a project management and bug/issue tracking system. Provides an interface to Subversion and an integrated wiki.
Prometheus - An open-source systems monitoring and alerting toolkit.