Well, since my last topic on Inventory display didn't go anywhere, let's get some thoughts on craft systems. Generally speaking, craft systems allow players to turn game objects into other (generally more useful) objects. Implementation can vary widely and I would like to see some opinions on what works, and doesn't work, in craft system design as well as interface. After all, the best craft system in the world is useless if hidden behind a horrible interface.
Ultima Online had a simple craft system that was enjoyable. For most crafts you had a required tool, material, and possibly external object such as a heat source. Crafting generally consisted of double clicking the tool, then clicking the material which would then either complete the task (such as heat on ore produces ingots or scissors on cloth produces bandages) open up a selection if multiple items could be produced by the action (say when forging ingots- you could make a variety of weapons and armor). The advantage was it was quick and simple, the downside is that it didn't really allow for much customization (though you could change colors certain thing afterwards with a dye tub).
Star Wars Galaxies has what looks like a neat system where you can gather all sorts of different raw materials that have different intrinsic properties that are used to craft components to build items. Since there are no "best" properties, different materials are better or worse for different applications. Additionally, there is a process for experimentation that apparently allows the crafter to modify the crafting even further. It all sounds very detailed, but I have never played so I have no idea if in practice it allows alot of variety, or just creates a tedious process.
Minecraft has an interesting approach to crafting. Like most games you gather raw materials to craft items. What is interesting about MC's approach is that items are formed based on the correct materials being laid out in a certain pattern on a crafting grid. The size of the grid also varies based on whether the crafter is utilizing a crafting table or not. Without it, he only gets a 2x2 grid, making only simple crafts such as torches, shears, and a craft table possible. It's also interesting in that raw ore is processed by placing it inside a smelter with fuel and waiting for the ore to transform into ingots. Cooking is done the same way (no ovens in MC :)).