Alex Mansfield

This plugin allows you to easily add code to your pages and posts without worrying about what the WordPress editor will do to it. You can embed HTML, video embed codes, Paypal forms, Google maps and more. Please note: this plugin will not allow you to run server side scripts such as PHP.
To use the plugin, all you have to do is create a custom field (you can name it anything), place your code in the new custom field, and place the following shortcode into your post where you want the code to go:
<pre><code>[easyembed field="name-of-custom-field"]
</code></pre>

Easy Embed

Allows any code to be easily embedded in posts and pages.

iSoftware

Blocks lets you create your own reusable blocks of content where you can use shortcodes to insert code snippets, HTML including forms, iframes, etc and control formatting.
You can insert Blocks into pages, posts, widgets or directly into php content.
It is ideal for inserting reusable objects into your content that you can use side by side or as an alternative to standard posts.
It is fully compatible with WPML for content translation and WP Views for content filtering.
Configurable Features:
<ul>
<li>The “Output Mode” setting to control whether block content is rendered adding paragraphs and line breaks (wpautop) or not.</li>
<li>The “Sort Order” setting to control sort ordering when quering for a list of blocks.</li>
<li>The “Block Widget” that allows you put a block in any widget area on your site.</li>
<li>The “Multilingual Block Widget” that extends the normal “Block Widget” to work in a multilingual context with WPML (requires WPML plugin and Block Type Translation enabled).</li>
<li>The “isw-block” shortcode enables a block to be embedded in any post on your site.</li>
</ul>

iSoftware Blocks

This plugin lets you create your own reusable blocks of content.

Easy Embed vs iSoftware Blocks