Snort
Snort ® is an open source network intrusion prevention and detection system (IDS/IPS) developed by Sourcefire. Combining the benefits of signature, protocol and anomaly based inspection Snort is the most widely deployed IDS/IPS technology worldwide. With millions of downloads and over 225,000 registered users Snort has become the de facto standard for IPS.
Ophcrack
Ophcrack is a Windows password cracker based on a time-memory trade-off using rainbow tables. This is a new variant of Hellman's original trade-off, with better performance. It recovers 99.9% of alphanumeric passwords in seconds.
Metasploit
Metasploit has become the de facto standard attack and penetration toolkit. Extremely extensible, and constantly updated to home in on the latest server and host vulnerabilities, Metasploit has the right stuff to test the perimeter of your network for holes, or determine whether your SQL or Web server or Unix, Linux, or Windows host can be compromised.
The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, full-featured, and Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as a full-strength general purpose cryptography library. The project is managed by a worldwide community of volunteers that use the Internet to communicate, plan, and develop the OpenSSL toolkit and its related documentation.
OpenSSL is based on the excellent SSLeay library developed by Eric A. Young and Tim J. Hudson. The OpenSSL toolkit is licensed under an Apache-style licence, which basically means that you are free to get and use it for commercial and non-commercial purposes subject to some simple license conditions.