Vagrant is a tool for building and distributing development environments.

A systems integration framework, built to bring the benefits of configuration management to your entire infrastructure.

Puppet, an automated administrative engine for your Linux, Unix, and Windows systems, performs administrative tasks (such as adding users, installing packages, and updating server configurations) based on a centralized specification.

Ruby DSL based software provisioning tool

Sprinkles for Apache, Passenger, Memcached, Git, Mysql or Postgres

See http://github.com/pitluga/supply_drop

Easy Ubuntu server setup via teleportation.

Rudy: Not your grandparents' EC2 deployment tool.

ESX Support for Chef's Knife Command

AutomateIt is an open source tool for automating the setup and maintenance of servers, applications and their dependencies.

Test-driven sysadmin.

Boris: A networked-device scanning library. Boris allows you to write programs for logging into and pulling information off of various server platforms, appliances, and other types of networked devices, producing clean and consistent data ideal for configuration managment usage.