Powerful bookmarx
By Percy Cabello
boox, a Firefox extension developed by martin, shines for a feature alone: it can display web feeds summaries when you hover over them in the bookmarks sidebar. And you can customize it to show the live/bookmark name, the web address, last visited, keyword, description, creation date and last modified date.
But boox does even more. It highlights live bookmarks containing new items plus it shows the complete web feed when you click on a live bookmark in one of five styles it brings along.
Give it a try at Mozilla Add-ons.