Alchemical Cauldron is a plugin for Bukkit, a wrapper for the Minecraft server.

How to install:
Put AlchemicalCauldron.jar in /plugins/.  Put a config.yml file in /plugins/AlchemicalCauldron/config.yml.

The config file looks like this:
log_level:  INFO
contraption_material: OBSIDIAN
fail_chance: 3
recipes:
    - product: DIAMOND
      type: item
      reagent1: COAL_ORE
      reagent2: OBSIDIAN
      reagent3: WATCH
      reagent3_consumed: false
    - product: COAL_ORE
      type: block
      reagent1: WOOD
      reagent2: COBBLESTONE
      reagent3: INK_SACK
      reagent3_data: BLACK
      reagent3_consumed: true
      
---snip---

contraption_material and fail_chance are not yet implemented.

Recipes are a yaml list of nodes, with some key/values:

product:  The name of the material to spawn.  See the org.bukkit.Material in the bukkit source for examples.
product_data: In the case of wool or dye, this is the color.  In other cases it may be durability or damage (not yet supported).
product_quantity:  How many to create.
type:     The type of recipe.  The options are: block, item, mob.
reagent1: Specifies the bottom reagent. It uses the same types as product, but only blocks are supported.
reagent2: Specifies the top reagent.
reagent3: Specifies the item the player might hold while right-clicking on reagent2.  This means it must be an item that can be in the inventory.  Many items simply will not work; experimentation will be required.
reagentX_data:  If the reagent X is wool or a dye, this is the color.
reagent3_consumed: true or false, whether to take away one of the player's reagent3s.  Defaults to true.
reagent3_quantity: How many of reagent3 are required.  This many will be consumed if reagent3_consumed is true.
secret: Whether to display the recipe in /recipes.

Also, I'm terrible at keeping this README updated, so there are probably recipe options implemented that aren't included here.  Read the source.

Some reagents don't work.  Sometimes this is because right-clicking on these blocks causes other things to happen (such as tool use) and sometimes it's a bug in Bukkit.  Open an issue if you find one of these.

How to use:
In game, build a cauldron out of OBSIDIAN (other materials may be supported in the future).
Cauldrons are a 3x3 (9 block square) layer on the bottom and a 3x3 ring (8 block hollow square) on top.

Cauldrons look like this:
 * Top:  Mid:  Bottom:
 * ***   ooo   ooo
 * *2*   o1o   ooo
 * ***   ooo   ooo
 * 
 * Key:	* = anything, probably air
 * 		2 = reagent 2, a placed block
 * 		1 = reagent 1, a placed block
 * 		o = obsidian

 Place the first reagent in the middle of the ring and the second reagent on top.  Right-click with the third reagent to invoke the recipe.
 
 
 
 Future ideas:
 - recipe failures with unpredictable results
 - recipe book manager
 - use of water/lava as a reagent
 - recipes that repair reagent3 or add even more durability.