Astroid is the new name of former logilab-astng library. It's an AST library, used as the basis of Pylint and including Python 2.5 -> 3.3 compatible tree representation, statical type inference and other features useful for advanced Python code analysis, such as an API to provide extra information when statistical inference can't overcome Python dynamic nature (see the pylint-brain project for instance).
It has been renamed and hosted to bitbucket to make clear that this is not a Logilab dedicated project but a community project that could benefit to any people manipulating Python code (statistical analysis tools, IDE, browser, etc).
Documentation is a bit rough but should quickly improve. Also a dedicated web-site is now online, visit www.astroid.org (or https://bitbucket.org/logilab/astroid for development).
You may download and install it from Pypi or from Logilab's debian repositories.