Rss_expander is a project mainly written in Ruby, it's free.
Expand on the fly truncated RSS feeds
To get rid of truncated RSS.
Example:
Original Feed: [http://feeds.feedburner.com/SecouchermoinsbetefrAnecdotes]()
CSS Selector: #content .mainBlock .blockMiddle
Expanded Feed: http://rss-expander.heroku.com/feeds/custom?url=http%3A%2F%2Ffeeds.feedburner.com%2FSecouchermoinsbetefrAnecdotes&selector=%23content+.mainBlock+.blockMiddle