Opbeat - Application monitoring for developers
Open PostgreSQL Monitoring - Oversee and Manage Your PostgreSQL Servers
ServiceTracer - Application Performance Monitoring
Errbit - The open source error catcher that's Airbrake API compliant
Guava - Google core libraries for Java 6+.
Redsmin - All-in-One GUI for Redis. Thightly crafted developer oriented, online real-time monitoring and administration service for Redis.