tcpxtract is a tool for extracting files from network traffic based on file signatures.
This is the homepage for the open source Seamstress seam carving library and Arachne, the seam carving program written to demonstrate the library. Seam carving is a technique developed by Shai Avidan and Ariel Shamir for resizing images by removing the boring bits.
An archive of free-to-download and use disk images for practicing your data forensics fu or testing file carving tools.
An excellent article from the Internet Storm Center about carving executables out of other sorts of files (like .rtf documents) for the purposes of identification and reverse engineering.