Resources

Operating System Tutorials:
Wiki Os Development
Bona Fide OS Development
Brans kernel Development Tutorial
James Molly Unix-clone Kernel Development
Brokenthorn Operating System Tutorials
The Operating System Resource Center
Operating System Tutorials


Kernels:
Brans Kernel
OSD Kernels
Sample Kernel (Demo kernel with basic screen)
Linux 


Toolsets:
NASM
DJGPP
MinGW
Cygwin
MASM
TASM


Bootloaders\Boot Sectors
GRUB

Other Resources
Intel Docs
IO Port List

ATA-ATAPI
ATA-ATAPI website

Video:
Official VESA Website 
256-Colour VGA Programming in C
Software Task Switching