Tutorials/Shelters

There are several things every minecraft shelter should have.

This is the single most important room and should be the first one built. A kitchen should include a crafting table, at least one furnace, and at least one chest containing key crafting materials.
 * A Kitchen

A room full of chests for storing all of the dirt, cobblestone and other materials that accumulates in your inventory while mining.
 * A Storeroom

It's generally a good idea to put the entrance to you mine inside your shelter. If you return at night, you won't have to make a mad dash to your house.
 * The Entrance to Your Mine

A room with a lava pit, for disposing of unwanted materials.
 * An Incinerator

or, if you would rather not risk fire or death, put a 3x3 pit (4 deep) with water sources in each corner, a sand block in the middle of the floor and a cactus on that

Since spiders can climb walls some form of a celling overhang is a good idea to have.
 * An Overhang

Other Ideas
There are any number of things to add to your shelter and here are just a few of them (ideas needed, don't feel shy to add stuff!):

1. Add underground floors to your shelter.

Using this gives you a chance to find resources and in the case of invasion by mobs it will always provide a safer spot.

2. Add aboveground floors to your shelter.

It is advised to normally do this after building underground floors if you have a lack of resources. This could even give you a chance to "snipe" some creepers and spiders in the morning.

3. Build a mob pit.

Basically a 3 wide and 2 down pit around your houses preventing mobs getting too close for comfort, and can later be expanded into a mob killer (requires lots of ladders).

4. Build a moat.

Don't they just look so cool in lava (don't forget to destroy all nearby wood :P ) (and water :P).

5. Make a farm extension.

Look at the farming tutorial for more on this. :)

6. Remake it out of a different material.

So much potential here!

7. Make a base in a new location.

Having more than one base helps if you need to travel farther to get resources. A base next to your spawn point is helpful if you built your main base somewhere else.

8. Add an escape tunnel.

You never know, that creeper might one day get you. Bonus points if the tunnel leads to your secondary base.

9. Make a panic room.

Put tnt throughout your base and have redstone leading to your panic room.

10. Make an underground farm and tree grower.

If you have a shelter underground, it might be a good idea to have these. Returning to the surface may be tough and dangerous.

11. Make an indoor animal farm

Works well if you built a large structure (such as a castle) on grass, simply light up the ground level and passive mobs will spawn inside your home every day, so you can hunt without any risks

12. Lava lamp

Simply make a hollow space out of glass and fill it with lava, an efficient method is to run a vertical collumn through many floors powered by a single lava block at the top. A word of warning, don't carry swords around glass containing lava, you never know when you might accidently bump that left mouse button...