from doron's blaahg: Livemarking your GMail Inbox

This is interesting, but currently quite useless:
FireFox has a feature called Live Bookmarks which essentially makes your bookmarks become an RSS feed reader.

Additionally, GMail has an undocumented feature providing XML feeds of your mailbox. Combine the 2 and you get: doron's blaahg: Livemarking your GMail Inbox

See the comments for why it's not quite so useful.