Computer Hardware Reference

formfactors.org
A site with detailed documents describing the current form factors used by makers of standard PC hardware. Includes the complete specs for ATX, ATX12V, BTX, microATX, FlexATX, TFX, SFX, and CFX
hardware book: connector menu
dozens of different computer connectors, explained and diagrammed. this is is a great reference resource.
sff committee - home page
Small form factor information repository. This is a web front end to an FTP server with small form factor working group documents.
source for 48-bit lba information
This site has info and tools you need to get big hard drives (over 130GB) working.
t13 technical committee - (atapi specs)
Technical Committee T13 is responsible for all interface standards relating to the popular AT Attachment (ATA) storage interface utilized as the disk drive interface on most personal and mobile computers today.