Specification sites
Operating systems
OS Development
Linux kernel documentation (drivers, irq, ...)
Operating System Engineering
Hardware
Guide to ATA/ATAPI documentation
Microsoft WDEV
Microsoft ACPI/Power management (hot plug&play, ...)
El Torito Bootable CD-ROM Format Specification Version 1.0 (January 25, 1995)
Fonts
TrueType Reference Manual (TTF)
TrueType typography (TTF)
Font metrics and glyph (explanation of terms)
Compiler
Evolution of a Java Just-in-Time Compiler for IA-32 Platforms
describing the idea behind JNode's l1a compiler.