This tutorial will walk you through creating a simple Google Chrome extensions that adds a button to a toolbar along the bottom of the browser window. First of all, you will need to be using either the developer channel of Chromium or else a recent trunk build. Once you're using one of those, follow these instructions to create and add a basic extension.

1. Create a folder somewhere on your computer to contain your work. For discussion, we'll assume the folder is located a c:\myextension, but it can be anywhere.
2. Inside this folder, create a text file called manifest.json and put this in it:

{
  "name": "My First Extension",
  "version": "1.0",
  "description": "The first extension that I made.",
  "toolstrips": [
    "my_toolstrip.html"
  ]
}

3. Add a text file to the folder called my_toolstrip.html, and put the following code in it:

<div class="toolstrip-button">
  <span>Hello, World!</span>
</div>

4. Find your chrome shortcut (for example, right-click the Chrome icon on your desktop and choose Properties) and add the --enable-extensions and --load-extension flags to it:

chrome.exe --enable-extensions --load-extension="c:\myextension"

5. Restart Chrome. You should see your button in a new toolbar along the bottom of the browser window.
6. Perhaps you would like it better if the button did something? Ok, create a new text file in the same place called hello_world.html, and put this code in it.
7. Now change the code in my_toolstrip.html so that it looks like this:

<div class="toolstrip-button" onclick="window.open('hello_world.html')">
  <span>Hello, World!</span>
</div>

8. Restart Chrome and click the button.
9. Do a little dance, you earned it!

Note: --enable-extensions is only needed while the extensions system is in development and will be removed.