EnCase is a suite of computer forensics software, commonly used by law enforcement. Its wide use has made it a de-facto standard in forensics. It is made to collect data from a computer in a forensically sound manner. Click Here To Download
The Sleuth Kit (previously known as TSK) is a collection of UNIX-based command line file and volume system forensic analysis tools. The file system tools allow you to examine file systems of a suspect computer in a non-intrusive fashion. Because the tools do not rely on the operating system to process the file systems, deleted and hidden content is shown. A graphical interface to the tools called Autopsy is available. Click Here To Download
Helix is a Ubuntu live CD customized for computer forensics. Helix has been designed very carefully to not touch the host computer in any way and it is forensically sound. Helix will not auto mount swap space, or auto mount any attached devices. Helix also has a special Windows autorun side for Incident Response and Forensics. Downloading of the live CD is only provided as a complement to membership in the e-fense members-only forum. An unsupported, older, no-cost version is available as well. Click Here To Download
Maltego is a forensics and data mining application. It is capable of querying various public data sources and graphically depicting the relationships between entities such as people, companies, web sites, and documents. Maltego is an open source intelligence too, but isn't open source software. Click Here To Download