Rafael Paulino

With this plugin you can place an iframe inside the TinyMCE text editor. 
You click a button in TinyMCE and a window appears to place the iframe data. 
Then just click on Ok and a shortcode is inserted with the iframe data and on the front the iframe is presented.
Com este plugin você consegue colocar um iframe dentro do editor de texto TinyMCE. 
Voce clica em um botão no TinyMCE e aparece uma janela para colocar os dados do iframe. 
Depois é só clicar em Ok e um shortcode é inserido com os dados do iframe e no front é apresentado o iframe.

Rafa TinyMCE Iframe

With this plugin you can place an iframe inside the TinyMCE text editor.

John Godley

PageView is a plugin that will display another web page inside the current post. This is achieved with the use of an 
iframe – an HTML tag that allows a webpage to be displayed inline with the current page.
To use:
<pre><code>[pageview url="http://urbangiraffe.com"]
</code></pre>
Optional arguments:
title = A title to show under the iframe 
desc = A description to show under the iframe 
width = Width of iframe, in px or % 
height = Height of iframe, in px or %
<h3>Documentation</h3>
Full documentation can be found on the <a href="http://urbangiraffe.com/plugins/pageview/" rel="nofollow ugc">Pageview</a> page.

PageView

Insert an iframe and display an external website directly in a post using just a shortcode.

Rafa TinyMCE Iframe vs PageView