Gmail has a great feature of offering feed for unread messages, which is currently not available in any webmail. This feature lets you to subscribe to RSS feeds of your Inbox. For using this service, you would need to use is http://mail.google.com/mail/feed/atom and the feed reader will need authentication. This wont work in Google Reader, but desktop readers like FeedDemon will support authentication.
Another feature of this feed is that you can subscribe to feeds of any label created in your Gmail account. To Subscribe to feeds of any label,
You need to change LABELNAME in the url with the name of the label in your mail box. This is also useful for browser feed reader like Firefox live bookmarks and Opera feed reader.