Secret of Mana
Secret of Mana has been partially hacked.
No known utilities exist specifically for editing Secret of Mana, aside from a number of Nightmare modules.
The SoM VWF Edition hack implements a variable-width font and some story dialog changes.
Many of the game's major data tables (weapons, armor, items, magic, etc) have been located. Map data is compressed in a format that has been partially solved, though special details (doors, event-based map changes, etc) remain unknown.
Another directory containing both information and some Java code concerning map compression