All of these plugins are supposed to work in version 2.5 and above. Also, as always, don't install all of these unless you want to decrease your blog's response time.
Additional Feed Content
Ozh' Better Feed - Allows you to add just about anything you want to your RSS feed entries such as links, ads, copyright information and more.
RSS Footer - Allows you to insert copyright information and link backs to your original posting in your RSS entries.
RSS Includes Pages - Allows you to include pages and not just posts in your RSS feed.
RSSupplement - Allows you to add a number of different things to your feed including comments link, social bookmarking links and more.
Simple Feed Copyright - Adds a simple copyright notice to the bottom of each entry in your RSS feed with a link back to your blog.
RSS Management
FD FeedBurner Plugin - Redirects your main feed, and your comments feed if you choose, through FeedBurner without any need to modify templates.
Feed Key - Allows you to add keys to restrict feeds to registered users.
Feed Wrangler - Allows you to manage your feed with ads, without, make some feeds bypass FeedBurner and more.
RSSless - Allows you to use short codes to remove certain types of content from your feeds such as videos or images that don't format correctly.
Stats
Feed Subscriber Stats - Allows you to see how many subscribers you have according to FeedBurner in your dashboard instead of going to their site or having to view your own site.
FeedBurner Widget - Allows you to add the FeedBurner chicklet directly from within your admin area.