The initial SOAP spec was pretty tightly coupled with HTTP. Shortly thereafter folks realized that this SOAP thing could apply to more than the HTTP request/response world. Great steps had been made to remove the HTTP dependencies from the SOAP and other, higher-level specifications, but we haven't made much progress in terms of creating other bindings (there is a 2-year-old "Email Binding" which is still just a W3C Note). Well here is a great start: SOAP-over-UDP which was published today by .
As Martin mentions, this plays a big role in things like auto-discovery of devices (as demonstrated by a couple of the co-authors: Lexmark, Ricoh. BEA is the other non-msft author). I see it also being big in publish and subscribe message exchange patterns. Probably the best part: it is a very simple spec.