In no particular order:
Dark Fiber for the OSdev FAQ, which really laid the foundation for these pages
Marven Lee for GRUB tutorial
Mark and Candace White for information on GRUB aout kludge
Martin Coleman for 16-bit NASM interrupt code
Tim Robinson, Beth Stone, and Stuart George for help with British keyboard layout
Tim Robinson for binary-kernel-with-PE-header hack
(chase[AT]osdev.org) for testing and fixing A20 code
Alexei Frounze for OS4D bootloader
Peter Montagner for information on Macintosh HFS+ filesystem
Craig Hart for list of PnP IDs
Gabriel Pickard for spotting errors in the IDT documentation
Julian Hall for pointing out the use of '$' with NASM identifiers with the same name as NASM reserved words.
Michael Cook for noting that ALL ASCII characters are legal in ext2 filenames, including the forward slash.
Jeroen van Bemmel, for helping with linker script to handle new ELF .rodata sections.
Craig Graham, Andrey Warkentin, and Fabio Alemagna for information about using C++ to make a kernel.
Brian Bruinewoud, for pointing out an error on the 'gotchas' page.