Yumani has published a nice tutorial on Sending Instant Messages via Mashup Server showing how to use the instant messaging capabilities built into the WSO2 Mashup Server.  I think the ability to have instant alerts as part of your mashup is a cool feature, and as Yumani shows in this article, they are pretty trivial to do.

I'm looking forward to adding the next step in a future release - the ability to invoke a mashup using instant messaging.  Then we'll have a scriptable platform for building agents that can communicate via IM.  Imagine converting your favorite service to an IM conversational interface.  Or making a data source available through an IM conversation.  Or even imagine new games...  Endless possibilities!