"Link to the Past" rom editor.
Although not yet completely finished, this surely is the Bible of the A link to the Past editing. It contains tons of useful and valuable information, written by practically everyone, who ever edited this game.
A commented trace log of the Zelda graphics decompression routine.
Contains extensive information on VRAM, SRAM, RAM, and ROM maps. The most comprehensive package of information available for the SNES version of the game.