MarcusPope

In the web marketing/publishing industry a content molecule is basically a piece of reusable content that can be placed throughout a website. Typically isolated in nature, they often appear in sidebars and margins. Applying this concept to the WordPress framework, you can create content that can be embedded anywhere shortcodes are processed. Taking the concept a little further, any number of custom attributes can be added to the usage of the shortcode, and those values can be embedded in the resulting output.
[m id=”slug” audience=”Student” product=”backpack”]
Will translate the following molecule:
Greetings {audience}! 
Check out our new {product} today!
into this:
Greetings Student! 
Check out our new backpack today!
Obviously a ridiculous example, but the flexibility remains the same regardless of the silly intent. Stop repeating content throughout your site only to have to re-edit those pieces in every location when you need to make a correction or update.
Molecules are a custom post type. After the plugin is activated a new section will appear in the left admin menu titled “Molecules.” There you can create and manage reusable pieces of content. As a bonus I have added the post slug to the list view for easy reference. If you embed a molecule in a post or page and the slug does not exist yet, it will create a draft for you to fill in later.
That’s about it for now, any input for future features is welcome.
<h3>Arbitrary section</h3>

Content Molecules

Enables the creation of reusable and dynamic content that can be embedded throughout the Wordpress platform via shortcodes.

bgentry

This plugin allows you to create custom content that appears in your WordPress posts depending on query variables in the URL. For example, appending \”?customer=yes\” to your URL can make the sidebar display the phrase \”We love our customers!\” while \”?customer=notyet\” can make the sidebar display \”Become our customer today!\”
The plugin includes a shortcode for insterting custom content into a page or post, as well as a widget for adding custom content to sidebars.
How to use: 
After installing the plugin, you will find “GET Custom Content” in your dashboard menu. 
There are just a few steps:
<ol>
<li>
Create a Variable. 
To create a variable, click “Custom Content Variables” under the “GET Custom Content” section of the Dashboard menu. Type a name for your variable, then click ‘add new variable.’
</li>
<li>
Create values for the variable 
Click “New Value” under the “GET Custom Content” section of the Dashboard menu. Type the name of your value in the post title field, and type some content. Then select the variable to which this value belongs in the “GET Custom Content Variables” box on the editor screen.
</li>
</ol>
If you want this particular value to be the default value, and therefore be shown when the variable is not defined in the URL, click the check box in the “Make this the Default?” box on the editor screen. It will appear if the variable is not defined in the URL (such as www.example.com) or when the variable is defined but the value does not exist (such as www.example.com?variable=nonexistent)
It’s up to you to make sure you don’t set up multiple values to be the default. If more than one value is set as the default, then whichever one is first when WordPress asks for the default will be shown as the default.
<ol>
<li>
Use the widget or shortcode to ask the site to load the custom content 
There are two ways to display custom content. One is to use the GET Custom Content widget to drop it in the sidebar. The second method allows you to load custom content in a page’s content using the shortcode, format [bg_gcc variable=”variableName”]
</li>
<li>
Create a URL. Just take a normal URL for your post or page, and add ?variablename=valuename and give this URL to people whom you would like to see your custom content.
</li>
</ol>
Detailed instructions are here: http://bryangentry.us/get-custom-content-wordpress-plugin/
<h3>How can I override the default content defined for a particular variable combination?</h3>
The default content for the variable is displayed when the variable is not defined in the URL, or it is defined with a value that does not exist.
If you want to override this content in some place, use the same pattern for overriding a variable/value combination (see answer to previous question), but use “default” instead of the value name. Example:
-value-default 
I want this shown instead of the default! 
-value-default
<h3>How can I insert the URL’s query variable value into my site?</h3>
Sometimes you may want to use value in the user’s URL to display something on your page. For example, you might want the link example.com/my-page/?username=Gretel to display “Greetings, Gretel!” on the page. To do this, enter a description for the particular variable (in this case, username) back on the screen where you can add or edit GET Custom Content Variables. Include VALUE in the spot where you want the value to be filled in. For example, you could type:
Greetings, VALUE.

GET Custom Content

Create dynamic pages using parameters in the url, such as example.com/my-post?username=Bob

Content Molecules vs GET Custom Content