Mining

Super Breaker
Super Breaker, while activated (by right-clicking with a pickaxe in hand), allows you to instantly mine blocks (when there isn't any lag that is) for a period of time depending on your mining level.

The duration of the skill starts at 2 seconds, increases by 1 second every 50 levels, up to 22 seconds at level 1000.

Cool down time is 240 seconds by default unaffected by level. This ability also allows you to triple the chance of getting double drops, though it does do more damage to the pickaxe you are using.

If the pickaxe breaks while this ability is being used, the player will suffer damage. Therefore a high durability pickaxe is recommended.

Blast Mining
Instead of using a pickaxe to break blocks, Blast Mining is done with TNT and Flint & Steel. This ability is activated by crouching and lighting TNT with a Flint & Steel. At higher levels the player will recieve Triple drops and no debris.

As the amount of drops gained from the explosion increases with your Mining level, so does the radius of the explosion. Damage taken by TNT lit with this ability is decreased, but not negated. Note that normally TNT drops 30% debris. Also, the blast radius of TNT increases at levels 250, 500, 750, and 1000.

Double Drops
Each time you level up in mining you get a 0.1% chance of getting 2 drops with every mine of an ore.

For example, a level 500 miner will have a 50% chance to get a double drop from one ore! Double drops works on all materials that are gathered fastest with a pickaxe (Stone, Ore, etc). Emerald ore however is yet to be added and as such will not yield double drops nor mining exp when mined.

The Smooth Stone Generator
Probably one of the easiest way to level up in this category is the Smooth Stone Generator and then have the stone pushing to you, then tape down left click or hold it down (ensure there is an empty space behind the smooth stone) then all you have to do is change picks as it goes. Convenient Inventory, which replaces your tool for you after it breaks with another from your inventory, is very useful. A nearby anvil could also be used to repair your tools and gain repair XP...Meshmeh

Coal, Iron, &amp; Redstone
The fastest way to train this skill is through mining coal, redstone and iron. These occur frequently on the map, are quite fast to mine, and give a decent amount of Experience Points. It is best to mine with a Diamond Pick as it has the most durability, and is able to mine any block that can reward experience. It is also recommended to level up the Repair Skill along with Mining as it can greatly reduce the amount of materials used on tools.

Netherrack Grinding
Another method is to mine Netherrack with a high-end pickaxe. Although it does not give much experience, there are vast amounts of it in the Nether and it mines incredibly quickly with a decent pickaxe.

You can also train repair by bringing five or so stone pickaxes and mine netherrack until each pick is almost destroyed, then go back and repair each one and continue. Of course, you could always bring an iron block and a supply of cobblestone with you.

End Stone Grinding
Yet another way is to tape down your mouse and W key in The End. This is somewhat risky as it is possible to fall off the sides, thus requiring the player to keep an eye at all times. End Stone gives you 150 XP each, resulting in a relatively fast leveling.

A modification of this is to mine down into the end island and excavate layers in 2 block high segments (Mine out 2 blocks, leave one above/below, mine out 2 blocks, etc.). This eliminates the need to deal with endermen and the XP will level you up quickly even at high levels. Works best with an efficiency 3 or 4 pick at least, and will give you tons of material to build stuff if that's something you want.

Obsidian Generator
There is a glitch where a player can generate obsidian from redstone dust (1:1 transformation ratio). If there is a flowing water block next to the redstone dust, (Dig a block below the flowing water so it doesn't flood the redstone dust.) and lava falls onto the redstone dust, the redstone instantly turns into obsidian. Since you did not place the obsidian, it is considered a naturally generated block. You do not have to place a lava source block on the redstone for it to create obsidian. The best method to exploit this glitch is to make a long row of redstone and convert all of it to obsidian. Use Super Breaker while walking sideways to rack in the XP.

Breaking nether portals also increases XP

Another fast way to level up with Obsidian is to destroy the Obsidian Pillars in the End, simply use a Ladder or pillar jump up, then once at the top, use super breaker or just mine all the obsidan until the bottom of the pillar.