Darik's Boot and Nuke
Self-contained boot floppy that securely wipes the hard disks of most computers. DBAN will automatically and completely delete the contents of any hard disk that it can detect, also prevents or thoroughly hinders all known techniques of hard disk forensic analysis.
HowStuffWorks: How Hard Disks Work
Takes apart a hard disk to see what's inside, and also discuss how they organize the gigabytes of information they hold in files.
Features for Apple's Time Capsule backup device and 802.11n Wi-Fi base station.
Hard Drive Help
Provides information and tips to solve common hard drive problems.