I made a mining system where you try to dig as deep as possible. Hopefully, this video explains it:
You use a pickaxe to dig, and every few blocks you get a mineral. If you dig on a specific spot, you will find a ladder to a new and often better mining level. To help you, this thing beeps when you get close to a new ladder:
The place is dark, so sometimes you need lanterns to reach the next ladder.
If you stay too long in a mine, it will collapse and you will lose your minerals. That's why you should always wear a helmet.
If you dig deep enough you might find one of the special levels.
The minerals and pickaxe graphics where made by some cool people and then posted in the Free Images thread.
You can try the script out without installing it. If you have access to Testbed, you can warp to mine_surface.nw. Otherwise, you can log on Maloria, which has a modified version of this script not too far away from the starting location (at the time of writing).