Buildout is a "system for managing development buildouts", according to its [http://pypi.python.org/pypi/zc.buildout home page]. While often identified as a ["Zope"] project, and indeed licensed under the ["ZPL"] by Zope creator ["Jim Fulton"], buildout is useful for configurations beyond Zope, and even, in rare cases, a few that have nothing to do with ["Python"]. The home page above includes extensive documentation, examples, and more.
[explain relation to easy_install and eggs]
["Martin Aspelli"]'s book on ["Plone"] 3 includes a good reference on buildout. Also, the Zope 3 Wiki includes a [http://wiki.zope.org/zope3/UsingBuildout useful page] on the subject.