glu is a free/open source deployment and monitoring automation platform.
glu is solving the following problems:
deploy (and monitor) applications to an arbitrary large set of nodes:
ensure consistency over time (prevent drifting)
detect and troubleshoot quickly when problems arise
glu takes a very declarative approach, in which you describe/model what you want, and glu can then:
Check the rest of the documentation for more details (including screenshots and diagrams).