The goal of this tutorial is to show multiple different ways for everyone, on modpacks, vanilla, or snapshot, to be able to share their worlds or creations from single player.
Part 1: Finding Your World Save
An easy way to locate your world save, regardless of modpacks or launcher, would be to start the game and go to the menu screen.
Click on "Options" then "Resource Packs" (or "Texture Packs" for 1.5, and directly on "Texture Packs" from the main menu for 1.4.7 and before; "Mods and Texture Packs" for beta versions of the game).
At the bottom left of the screen, there should be a button called "Open Resource Pack Folder". Click it. A folder window should open up.
The window should look something like this:
Go up one level to your ".minecraft", "minecraft", or modpack's main folder, then open the saves folder.
You should see something like this at the top of the window:
If you are vanilla, you should see a ".minecraft" before "resourcepacks". You should see folder names with arrows around them, telling you were you are on your hard drive. Click on the folder name before "resourcepacks" or "texturepacks", in this case, you would click on ".minecraft".
If you were on Tekkit Main from the Technic Launcher, you would see:
In this case, you would click "tekkitmain", since that is the enclosing folder.
You should now see something similar to this:
Double click on the "saves" folder to open it.
At the top left of your window you should see something like this:
You want to click and select the third option, "column view".
Your window should now look something like this:
In the same column as the folder "resourcepacks", there should be a folder named "saves". Click on that. If you wish to return to normal folder view, you can return with the button(s) shown above for changing folder view.
Part 2: Preparing the World for an Upload
Find the world that you want to upload in your list of worlds. The world is a folder, usually with the same name as the world in-game. If you ever renamed the world, the folder will keep the world's original name.
You will want to compress the world so you can send the world, rather than a group of files.
To do so, there are different ways to do that based on your operating system.
Right click on the world folder and select archive/compress.
This .zip file will be the one that you will upload.
For windows, only one of them will work. The other will not.
Windows (Way 1):
Right Click on the world folder and under the drop-down for "Send to", click "Compressed (zipped) folder"
The zipped file will be called "worldname.zip"
Windows (Way 2):
Right click on the background of the folder, and under the drop-down for "New", select "Compressed (zipped) folder". Drag and drop your world onto the new zipped folder. Rename it to your world's name plus ".zip" at the end, so should be "worldname.zip"
IMPORTANT STEP: MOVE YOUR "worldname.zip" TO YOUR DESKTOP SO YOU CAN FIND IT TO UPLOAD!!!
Part 3: Uploading Your World
Dropbox (Dropbox account required; Convenient; Max 2GB + 1/2GB per referral, up to 18GB):
Easiest to use (with desktop application). Quick and easy (until you are out of space).
Click Here to start out with 2.5GB instead of 2GB. (I think, not too sure)
If you have the desktop app, just drag into the dropbox folder. Right click on the "worldname.zip" and click on "Copy Dropbox link". The link to the world download will be copied to your clipboard. The link wont work if you are out of Dropbox space. Link may be removed if it is used too much, this is mainly for sending to one or two other people.
Google Drive (Google account required; Max 15GB):
A little harder to use, but there is a lot of space, and if you run out, you can make a new account, or pay $1.99 per month to get another 85GB (100GB total).
Go to Google Drive. In the top left corner, click "New", then "file upload". Select the file, and upload it. To get the shareable link, right click and click "Share..." and NOT "Get Shareable Link". In the bottom right corner of that popup window, click "Advanced". Under "Who has access", to the right of "Private - Only you have access", click "Change...". Change it to "On - Anyone with the link". Then click save. There should then be a link highlighted, copy that. That is the download link.
MediaFire (MediaFire account required; Max 10GB):
Most people use this for mass distribution of Minecraft worlds.
I am not too sure how this works, but once you have an account, you upload it, and it gives you a link to download it.