shprung

Less than 40 lines of php code so it will not slow your site and if all you 
need is to add an rss feed, give it a try.
You can even setup the output template – something many other plugin don’t 
offer.
<h3>A brief Markdown Example</h3>
<pre><code>short code examples:

[rss url="http://www.usacycling.org/rss/headlines.rss"]


[rss url="http://www.usacycling.org/rss/headlines.rss" no="20" target="_self"]

You can change the template used via wp-admin/options.php , look for
'rss_shortcode_template'
Template fields documentation:
 _TITLE_ : the rss feed title line
 _LINK_ : the link to the complete store, aka permalink
 _MSG_ : the short message/description; the first few 
 lines of the post/story
 _DATE_ : post date & time
 _TARGET_ : the link target
</code></pre>

RSS shortcode w/template

lets you embed rss feed in any WordPress content (e.g., pages, posts, custom post types) using Shortcode.

bkmacdaddy

Aida B.

leepettijohn

Dee Teal

This plugin allows you to place a widget on your sidebar that fetches the most recent contents of a Pinterest user’s RSS feed and displays the corresponding thumbnail images. You can choose whether to show the description below the image, and you can set the height and width of the thumbnails to fit your theme. You also have the option of showing 4 different sizes of the official “Follow Me On Pinterest” button below the list of your pins.
You can also use this plugin from your theme templates, to display images lists anywhere else on your blog and you can easily give them a fixed size or a maximum size with CSS styling.
Starting with plugin version 1.3, you can also add a list of thumbnails of your Pins to a post or a page in the editor using the shortcode [prw username=”Your Pinterest Username”]. (See FAQs for instructions).
Version 1.4 adds the capability of showing pins from a specific board in the widget or shortcode, rather than just all of the latest pins from a specific user. (See FAQs for instructions).
Note: This plugin is heavily based on the Image Feed Widget plugin created by Yorik van Havre (https://wordpress.org/extend/plugins/image-feed-widget/). As of version 2.0 it also utilizes the jQuery NailThumb script for image resizing (http://www.garralab.com/nailthumb.php) and no longer utilizes the timthumb.php script.

Pinterest RSS Widget

A widget to display thumbnails and titles of the latest Pinterest Pins from a specific user via their Pinterest RSS feed

RSS shortcode w/template vs Pinterest RSS Widget