viperchill

ViperFeed adds a gorgeous footer to your RSS feed. This will be displayed for people who get your blog posts via email, or in an RSS reader like Google Reader and Bloglines. You can use this space for giveaways, encouraging comments, showing ads, or linking to other areas of your website.
<a href="http://www.viperchill.com/" rel="nofollow ugc">ViperChill</a>, a blog on Viral Marketing, is the creator of this plugin. If you want to take your blog to the next level, you should read this post on <a href="http://www.viperchill.com/wordpress-seo/" rel="nofollow ugc">WordPress SEO</a>.

ViperFeed

ViperFeed adds a gorgeous footer to your RSS feed. This will be displayed for people who get your blog posts via email, or in an RSS reader.

jneuveglise

This plugin will cut your RSS feeds at the “more” tag. It will enable you subscriber to see what you want them to see as on the home of your blog.
It will also add a customizable link at the bottom to the complete article and optionally a fully configurable footer to avoid robots to steal your content.
It will not work if you choose ‘partial’ feeds in the WP configuration.

RSS No More

This plugin will cut your RSS feeds at the 'more' tag or custom [rss-cut] tag and optionally append a footer to each article on your RSS fee …

ViperFeed vs RSS No More