An open source utility for Windows (32 and 64 bit) that will securely erase files and directories on a Windows machine, in addition to scrubbing free space and OS-related temporary files that could leak information. It can even wipe an entire system if you need it.
A freeware utility which clones most any hard drive block by block to another device. Possibly crypto agnostic.
An archive of free-to-download and use disk images for practicing your data forensics fu or testing file carving tools.