Metasploit Project

The Metasploit Project is up to version 2.3 at the time of this post. Metasploit provides IDS signature development, penetration testing, and exploit research.
There is a tutorial by Impact at AbsoluteInsight that goes over Metasploit version 2.1. Older version, but the tutorial covers a lot of insight on penetration testing and how exploits work.

Note that Metasploit is a known research project and use of it can be tracked. Do not attempt to access systems that you do not own and only use for legal penetration testing and research purposes.