With serverspec, you can write RSpec tests for checking your servers are provisioned correctly. Serverspec tests your servers' actual state through SSH access, so you don't need to install any agent softwares on your servers and can use any provisioning tools, Puppet, Chef, CFEngine and so on.

(via Dave Doran)

well-written, and it's good to see version control listed right at the top of the list. But quite dead; interesting for historical reasons only at this stage