Live Bookmarks are a feature that have been included in Firefox for ages, and have provided a simple way for you to subscribe to RSS feeds. They essentially act like dynamic bookmarks that are able to update as websites offer new content, and the Feed Sidebar extension makes it even navigate through the news they bring to you.
Once installed you’ll notice an RSS button in your Address Bar, and when pressed a sidebar will appear. From there you not only get a nice interface for glancing through your Live Bookmarks, but you also get some additional features. You can perform instant searches on news items, mark items as read, change the update interval, or see a brief preview (a few sentences) by single clicking on an item. All of this contained within your browser’s sidebar.
There are obviously feed readers that do all of this stuff and a lot more, but I know quite a few people who use Live bookmarks merely because of their simplicity. This extension retains that simplicity while making reading new items a tad easier. If you’re already using a dedicated RSS reader my guess is that Live Bookmarks (even with this extension) will seem underwhelming, otherwise it’s worth giving a try.