Have you subscribed to feeds of any other blog? Have you ever viewed the entire feed mail?
If so, for the feeds of some blogs, you can find some sharing buttons like this

So, this post says you how to add this buttons to your feeds.



STEP-I:
Go to your Feedburner account


STEP-II:
In the optimize tab, go to feed flare option

STEP-III:
Check the buttons you want to display in the feed mail

you can see the preview in the same page



STEP-IV:
You can rearrange the buttons in the way you want and after all get set, click on save button.

That's it. Your new feed mail with sharing buttons is ready to use.