Amazon Simple Queue Service. This is so satisfying. If I was a smoker, I'd step outside for one right now with a copy of this under my arm and a coffee.
Simple Queue Service is the sort of hosted web service that makes sense to me as an application developer. I would use it in its "*on* the web" mode of course by means of the RESTian interfaces. I'd also be willing to bet real money that the RESTian uses of this facility will be streets ahead of the soapy wsdls uses. All we need is to coalesce around a simple HTTP pattern for reliable message exchange and we are off and running. I'll be posting one of these soon as part of my five-part Jython tutorial.
Look out for a slew of interesting stuff on top of Amazon Simple Queue Serice. Also look out for other vendors - lemme see...search engine providers for example:-) - offering similiar pay-as-you go distributed computing plumbing services in the years to come.
If you are not familiar with asynch messaging as a distributed computing paradigm, now would be a good time to get reading. this would be a good place to start.