Learn how to operate the world's first fully electronic digital computer in this helpful instructional video. No, not ENIAC - the Atanasoff Berry Computer. Here's an operator's manual. More information about the reconstruction.
The Red Hill Guide is an amazingly detailed and well-written compendium of desktop hardware old and new, with a focus on PC and x86 compatibles. Look for your first CPU, hard drive or mainboard.
Twenty years of Macintosh - a well done retrospect about the Apple Macintosh presented in a series of posters, annotated with excellent topical links for further reading.