ABC Manual (2005)
Based on the now dated AT90S8535 AVR microcontrollers, the Investment Technologies' (now defunct) ABCmini and ABCmaxi boards gave hobbyists and professionals alike the power and flexibility of the Atmel AVR ICs. I became frustrated at the lack of documentation provided with said boards however, and that spurred me to write my own.
Writing as I discovered and learned, the manual grew to over forty pages. The makers of the boards, Austrol Pty Ld. were so pleased with my manual that they sought permission to make their own revision for their website. Since the company folded, this is no longer available - the original and unofficial version can be downloaded here.