Treegger has launched a service allowing Twitter users to chat in real time using an XMPP client such as Miranda, Pigdim, Adium, iChat (see the list here).
Messages exchanged during conversation are not stored or published on the web or anywhere else.
Bidirectional relationships (people followed and following you) are set as chat friends so if you are a massive twitter user with tons of followers don’t expect to see them if you are not following them. Unfortunately, this service is probably unusable with classic client software if you have thousand of bidirectional relations.

Before anything else I would like to say that this is a great article! It doesn’t only help people but it also provides information to a lot of people regarding tweeting. Instant messaging using Treegger is really great because people will not only be able to tweet what they are doing but they will be given instant access in instant messaging when it comes to additional question and queries. Now people will get feedbacks and answers from tweeters in the fastest way ever.
Thanks for sharing this!
Alex