Holy crap - XMPP support in AppEngine now! Now AppEngine has a real-time communication infrastructure.

Quoted: Tatango provides free group text messaging and group voice messaging to connect any type of group via their mobile phones.

Free online meeting software - send screen captures or screencasts to users over the web.

Chat Patent - issued 2006 - this looks like a continuation/split from the original 1996 patent.

SigGraph research paper describing Comic Chat (August, 1996).

Google Talk API's

I'm using two tools from our StartPad tenants - RescueTime and Chatterous. I think they're both really cool and useful.

Twitter uses the model of a single monolithic service which attempts to become a central hub for all personal "event" messages. As we are seeing, this is a very challenging scaling problem.

There is some standardization work going on around "XMPP" - which started as an IM protocol (person-to-person), but has added extensions to support "publish-subscribe" (PubSub) and "Personal Eventing" (PEP).

I think a distributed system, more like email, may be a more sustainable way to deliver the Twitter-like services that people desire. There will still need to be centralized servers that support "tracking" - so people can subscribe to updates for groups or tags.

Unfortunately, Twitter-like functionality has N^2 scaling characteristics (since each Tweet generates a message that has to be transmitted to each follower). So any architecture designed to handle the load will have to efficiently manage the collection and then distribution of all of these messages.

Extensible Messaging and Presence Protocol (IM protocol)