Writing up the first level of my tree-trunk megadungeon for my art competition winners, I hit upon the idea of using Excel as a megadungeon key. Viz [DON'T LOOK AT THIS IF YOU ARE A PLAYER IN MY GAME AND DON'T WANT SPOILERS]:
Hence, each sheet within the Excel file is a level of a dungeon (in this case, the only sheet visible is 'Fair Folk Level 1/Woodwoses'), divided into four columns.
The first column (the only one that I find slightly awkward/ungraceful) is a description of general conditions in the level.
The second is the random encounter table (using 2d6, natch).
The third logs the different entrances.
The fourth is the key itself.