Google Reader is probably the most popular RSS agregator service but it lacks an official desktop client but for that you can use Desktop Google Reader (unofficial client) who's major feature is Outlook-like notifications for new items arriving for any of your feeds. For now, it's features are very basic (like viewing/deleting & starring functionality) but it will hopefully grow into something more functional.
Download Desktop Google Reader | via BlogsDNA
Download Desktop Google Reader | via BlogsDNA
