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.

danikoo

NEW: 
1. added – option to choose multiple post types, example: ?call_custom_simple_rss=1&csrp_post_type=page,post 
2. added – option to choose multiple post status, example: ?call_custom_simple_rss=1&csrp_post_status=publish,draft 
3. added – better documentation (tutorial).
A plugin to create a your own Custom Simple RSS Feed 
according to parameters you choose!
*** the best solution for using MailChimp RSS campaigns ***
in simple words: 
Ever wanted an rss feed for just a specific Author and specific Category?
Or Even an rss feed for a specific Custom Field ???
Well… now you got it !
The plugin does not alter your default wordpress feeds – it enables you to display feeds on the fly via specific url with pre defined url query parameters.
for example:
display only 5 items from specific category order by name descending:
www.yordomain.com/?call_custom_simple_rss=1&csrp_posts_per_page=5 
&csrp_orderby=name&csrp_order=DESC&csrp_cat=4
Filter items by:
<ul>
<li>category id</li>
<li>post type</li>
<li>post status</li>
<li>tag</li>
<li>range of dates</li>
<li>and even meta keys and values!</li>
<li>NEW! filter by custom taxonomy</li>
</ul>
Order by:
<ul>
<li>name</li>
<li>date</li>
<li>author</li>
<li>ID</li>
<li>etc</li>
</ul>
More Features:
<ul>
<li>number of items to return</li>
<li>pagination </li>
<li>show post thumbnail or not?</li>
<li>set post thumbnails size to display?</li>
<li>show post custom fields (espically usefull if your using your rss as an affliate feed)</li>
<li>filter by date published or modified</li>
</ul>

Custom Simple Rss

A plugin to create your own Custom Simple RSS Feed according to parameters you choose

RSS shortcode w/template vs Custom Simple Rss