Give the plugin a remote RSS/Atom feed, or maybe just some XML, and get the data back to use in your templates.
{% set feed = craft.feeder.getFeed('http://feeds.feedburner.com/workingconcept') %}
{% set posts = feed.channel.item %}
{% for post in posts %}
<h3>{{ post.title }}</h3>
{{ post.description | raw }}
{% endfor %}
Drop the feeder folder into craft/plugins, then visit the Plugins section of the control panel and install.
The plugin uses Craft's included Guzzle library to pull the URL you provide, so if things don't go well it's probably because of a bogus feed URL, a poorly-formatted feed, or something Matt overlooked during his five minutes of testing.
GitHub issues and pull requests welcome!