Part of the Take It Outside hangover: I was saying I'd like to loop back 20 years and reimplement MUDs using Instant Messaging. So I hacked up a primative interface to explore Cal's London tube map station-by-station via AIM. You can't access it I'm afraid, you'll just have to trust me that it feels surprisingly claustrophobic when you're lost, and very vivid. So what next?
In Iain M Bank's Culture novels (good scifi) the ships are enormous AIs, massively intelligent. They communicate using proxy avatars, being that appear to be people but are actually shells proxying the ship's presence and intellect to the human scale.
Weblogs (internet services more generally) should be represented as avatars hanging around the IMvironment, near the tube stations the authors are physically located. Speaking to them, you should be able to pass notes to the weblog author, query the avatar for a RSS feed rendered as in-game speech, and ask questions which are piped through the weblog search engine. The avatar acts as a memory holding pen for communication to/from the author, and can expand beyond just an alternative interface to a companion of sorts. A know-all buddy. Simpler avators would be like talking mice you (as character) could carry around in your pockets. They'd tell you of latest posts to the weblogs they represent, and pipe up to your questions.