Instrumental
Instrumental is a real-time, high-scale application and server monitoring tool with intelligent alerts, a powerful query language, and free development accounts.
linux windows oxs free metrics commercial metrics monitoring visualization php ruby python net java nodejs
jclouds
A Java Library for controlling cloud resources, with various plugins for many popular cloud providers.
linux windows osx open-source cloud-paas java
KairosDB
KairosDB is a fast distributed scalable time series database written on top of Cassandra. RESTful JSON-based query/results. Includes flot-based visualization.
linux windows osx open-source metrics visualization java cassandra
SSH KeyBox
An open-source jump box solution with auditing capabilities
linux open-source cloud monitoring security java