Alexandru Vornicescu

If you want to resize featured images (post thumbnails) on the fly for your posts automatically then this plugin can help you.
To take effect just open a post or page and all featured images in that post will be resized to a normal size.
This plugin can be very useful after a theme install.
It can be an alternative for Regenerate Thumbnails plugin.
I think this plugin is better because you will not need to wait before all images are resized for all different sizes, just for images that are need to resize.
The plugin will keep the original copy of all image files.

Resize Post Thumbnails

This plugin is very useful and time-saving! Works fast and doesn't need any extra steps.

Best alternative to Regenerate Thumbnails

This plugin will resize post thumbnails on the fly.

Greg Ross

A quick and easy shortcode to embed iframe’s that resize to the content of the remote site.
Auto iFrame shortcode is in the format of:
<pre><code>[auto-iframe link=xxx tag=xxx width=xxx height=xxx autosize=yes/no]
</code></pre>
Where:
<ul>
<li>link = the url of the source for the iFrame. REQUIRED.</li>
<li>tag = a unique identifier in case you want more than one iFrame on a page. Default = auto-iframe.</li>
<li>width = width of the iFrame (100% by default). Can be % or px. Default = 100%.</li>
<li>height = the initial height of the iframe (100% by default). Can be % or px. Default = 100%.</li>
<li>autosize = enable the auto sizing of the iFrame based on the content. The initial height of the iFrame will be set to “height” and then resized. Default = true.</li>
<li>fudge = a fudge factor to apply when changing the height (integer number, no “px”). Default = 50.</li>
<li>border = enable the border on the iFrame. Default = 0.</li>
<li>scroll = enable the scroll bar on the iFrame. Default = no.</li>
<li>query = pass the parent’s page query string to the iFrame. Default = no.</li>
</ul>
Note: Auto re-sizing of the iFrame for cross domain sites does not work, this is a security protection provided by the browser and there is no way around it.
Now supports (Shortcode UI)[https://github.com/fusioneng/Shortcake] (aka Shortcake)!

Auto iFrame

A quick and easy shortcode to embed iframe's that resize to the content of the remote site.

Resize Post Thumbnails vs Auto iFrame