Morgan Kay

If you use a service such as Feedburner or MailChimp to turn your RSS feed into an email subscription, and the images in your posts are more than 600px wide, the formatting of your HTML emails might be messed up. This plugin lets you resize the images in your RSS feeds.
Version 2.0 has been completely re-written from scratch! It is now more reliable, and works with images from external URLs.

RSS Image Resize

Resize images in RSS feeds so they will fit in HTML emails.

Mark Howells-Mead

joelmelon

Adds the post thumbnail to the RSS feed using the XML tag specified in the <a href="http://www.rssboard.org/media-rss#media-content" rel="nofollow ugc">Media RSS Specification</a>, as well as an <code>IMG</code> tag in the RSS content.

Add post thumbnail image to RSS feed

Adds the post thumbnail to the RSS feed using the XML tag specified in the Media RSS Specification, as well as an IMG tag in the RSS content.

RSS Image Resize vs Add post thumbnail image to RSS feed