When Google Reader announced it was shutting down, I moved to Tiny Tiny RSS. In Tiny Tiny RSS, the standard action for opening links in a new tab also raises the tab, interrupting your consumption of the feeds.
This Firefox extension lets you configure a shortcut key to open items in a background tab. In conjunction with the googlereaderkeys Tiny Tiny RSS plugin you can have a pretty efficient process for reading feeds.
Note that the extension uses the "sync" storage area to store settings. You must enable synchronization of "Add-ons" in Firefox to configure and use this extension.
Released under the MIT license.
