While we do not offer a way to directly consume an RSS feed and display it on your site, there is a way to embed a third party service, such as feedburner, into a Simple Text sidebar.
1) Locate the URL of the feed you want to use.
3) Activate "BuzzBoost" within feedburner.
(To use BuzzBoost, navigate to the Publicize tab for your feed and select the BuzzBoost service from the menu on the left. Set BuzzBoost options the way you like, then click Activate )
4) Copy the code snippet from the BuzzBoost page
5) Create a Simple Text sidebar, paste in the code.
To the right is an example of an RSS feed in the sidebar.
Any feed service that provides you with output code will work in a similar fashion - this is only one example.