I'm trying out an interesting arrangement for my wilderness encounter tables (mentioned in my previous post). I have a table for each terrain type: clear/grassland, forest, hills/badlands, mountains, desert/barren, swamp/marsh, jungle, river/lake, ocean, arctic, settled, city. For each table, there are five columns (six with numbering) and twelve rows.
The columns are Animal, Human, Common Monster, Unusual Monster, Rare Monster. These are determined by a d12 roll: Animal 1-3, Human 4-5, Common 6-9, Unusual 10-11, Rare 12. A few terrain types get some adjustment to the number spread, but that's the basic.
I haven't filled out the monsters in any of the tables yet, but I have 12 slots for each. If there aren't enough suitable creatures, I can double some up or adjust the rarity. It doesn't give quite as much variety as Mentzer's charts, but 60 creatures per terrain type should be enough for a general table.
Oh, and these twelve tables only took up three columns of my 2-column layout, so I had room for tables for the Planes: Elemental, Ethereal/Astral, Upper, and Lower. These are arranged a bit differently, but I think it will be handy to have some random charts for planar adventures if I don't have anything worked up for a specific plane.