For my weekly game, I have an old dwarven shrine to detail and flesh out and present on Sunday. Straightforward.
For the secondary campaign... with the OD&D rules hack... well... that's turned into a ridiculous project. Here's where I am with it:
Character creation and definition is done. Seven classes: Fighting Man, Magic-User, Cleric, Dwarf, Hobbit, Elf, and Gnome. 3d6, down the line, with original box ability score bonuses (ha!).
The demi-human classes have little bits to make them... different: The Dwarf is from Dragon #3, with my adding in that they can not use magic items at all, and I'm wondering whether I am going to make them completely immune to magic at all as well. This would mean healing spells and potions don't work either, so it's not just an easy choice to avoid fireballs. The Hobbit is basically the Thief class from Greyhawk with some flavor added. The Elf is the Druid class (so they get a different spell list than mages), with elfy flavor, with the added restriction that they absolutely may not touch iron or steel, and take damage if they do. The Gnome is the illusionist class, and able to cast spells if wearing magic armor.
Money will use a silver standard. Beginning money is 3d6x10 sp. But... the prices remain in gold pieces as they are. Beginning adventurers will be running around with spears and leather armor, hoping to win enough loot to buy such a grand weapon as a sword, and then the impossible dream of a horse and a suit of plate mail armor... All of the treasure tables have been shifted so what used to be sp are now cp, gp are now sp, pp are now gp, and the old electrum and copper columns went bye-bye. Gems and jewelry retain their gp value though.
XP will be awarded as the original box set states. It's a little bit more bookkeeping, but nothing too big. I like the idea that a 5th level guy can adventure with a 2nd level guy and the 5th level guy, even with an equal split of gross XP, nets far less than the 2nd level guy. This will be for monsters only though... gold will still be on a 1=1 basis to prevent "No, no, when we ran I only dropped the orc loot, not the minotaur loot!" arguments. OD&D experience point bonuses for prime requisites (gnome = CHA, hobbit = DEX, dwarf = CON, elf = SOL).
Combat will be the Man-to-Man system in Chainmail, initiative determined by weapon speeds and all. To handle combat with monsters, I'm adding a few armor types to the table and a few monster attack types, with easy conversion notes (1 - 3HD monsters with claw attacks use Claw 1, 4-7HD use Claw 2, 8+ use Claw 3, for example). I need to get away from the "Alternate Combat System" altogether with this campaign. All HD and damage dice are d6.
Most of the actual rules (not like OD&D gives many... :P) will come from Mentzer and Labyrinth Lord, depending on what I find easier.
The spell lists are directly from the AD&D Players Handbook (not enough choice and detail in the OD&D books), with lots of editing made (thank god for pdf cut and pasting). Gone are all mentions of segments and components and damage is all converted to d6s. Clerics have absolutely no direct offense spells now (and Blade Barrier becomes the Barrier spell from the Mentzer versions). I nearly just used the Mentzer version of the spells, but with a piss-poor Druid (Elf in my campaign) spell list and nothing for Illusionists (Gnomes), it would look crappy to take half the spells from one source and half from another. Oh, and everyone must keep spell books. Or "prayer books" in the cleric's case.
Magic items will be a mix of Mentzer (weapons and armor from the Expert and Companion rules, for sure!) and AD&D (miscellaneous items!), edited to conform to the above rules changes. All random tables changed to bell-curve probabilities so things like potions and scrolls will really show up a lot more.
Mentzer monsters for the most part (they seem easier to convert for my purposes, and boy do I love the Morale stat being right there), and then a modified version of my Creature Generator (to take into account the different way I'm handling monster attacks and armor in this campaign) for anything wild...
It's been a most edifying journey these past few weeks of flipping between AD&D and OD&D and Mentzer and Basic Fantasy RPG and OSRIC and Labyrinth Lord and Chainmail to put together my ultimate little D&D of my own. Comments and suggestions please.