http://www.mod-buildcraft.com
http://minecraftbuildcraft.wikia.com
http://www.youtube.com/user/SpaceToadCraft/videos
For a better explanation of the basics, see the tutorial on pipes, tutorial on engines, tutorial on machines 1, and tutorial on machines 2.



In short, there are 3 parts: Engines, pipes, and machinery. Pipes can be used to transport fluids (lava, water, etc) and items, engines power pipes and machines so they work, and machines can do additional tasks such as automated crafting / smelting, automated mining, and automated building with blocks... inputting / outputting items through pipes in order to do so. Engines and pipes can be crafted in different variants (wood, stone, iron, gold, etc) each having a property and / or improvement over the other. Engines work faster the more you leave them running, but also acquire heat (indicated by their color) and can explode if not cooled.
Now that Minetest can be modded, I would really love to see a version of this mod for it too. I thought about trying to do it myself, but I'd at least need examples of some LUA functionality before I could think about it. I'd rather leave it up to an experienced user who can do it better than me however. I should be able to create some good textures at least, once I know where and how everything goes.
I know Minetest is still in a basic stage. But if my understanding is correct, the existing LUA hooks should work with many features that would be needed for such a system. These would mostly include checking object connections (like redstone works, in order to tell if two things are connected at the same end of each pipe), having blocks which are placed on the ground being able to mine / create other blocks, and having the system capable of either dropping items or putting them in connected chests. Maybe a few more script hooks would be needed later on.
I'm not suggesting that we create something as complex as Buildcraft from the beginning. I'm mostly interested in a system that can do its basics. That means engines which can run on different types of fuel (similar to furnaces), and that can overheat and eventually explode or break. Next we'd have pipes, which items can flow through when they're powered by engines. For starters, the pipes could connect from chest to chest, and transport items in between. Then on the list of machines, the simplest one that can be done now would be a mining well, which breaks blocks under it and places them in the nearest pipe or drops them on the ground. Later on, we can add pumps as well, when / if the fluid system in Minetest will allow it.
I imagine such a thing would be both very fun to create, and very fun to play with afterward (especially on multiplayer servers). So does anyone experienced with modding Minetest wish to adventure on this boat? I can't promise I can help much (except tweaks and minor things), unless I have clear examples I can duplicate or otherwise understand. Anyway, I'd like to hear if anyone else wants such a mod, as well as who's willing to help and get things started.
