We’ve already highlighted how to subscribe to RSS feeds of your Gmail labels, but the Google Operating System also points out how easy it is to subscribe to a feed of all your unread email using the built-in
unread label. In essence, you’d just add the following URL to any feed reader that supports authentication (of which Google Reader is not one):
The really cool part of this feature is that you can open the email directly in Gmail from the item in your newsreader. Just remember, if you're subscribing to your Gmail unread feed in a newsreader that makes feeds public, be sure your privacy settings are properly configured so you don't end up sharing any of your private email messages.