Here are some documents on SNES, mostly technical stuff, some good for hacking like the register summary. They are still really interesting in most cases, as long as you like the technical side of the SNES.
Edit: The documents are hosted on Goolge drive, so no Google/Gmail account, no document!
SNES Registers (Summary)
SNES Register (CPU)
SNES Register (PPU)
Sony SPC-700
W65C816S Microprocessor
SNES Programming Book I
SNES Programming Book II
SNES Software Manual
Edit: The documents are hosted on Goolge drive, so no Google/Gmail account, no document!
SNES Registers (Summary)
SNES Register (CPU)
SNES Register (PPU)
Sony SPC-700
W65C816S Microprocessor
SNES Programming Book I
SNES Programming Book II
SNES Software Manual