[eluser]WanWizard[/eluser]
I have used it on a corporate project (where Oracle's SOA suite provided the message queues).
It is useful in situations where you need inter-process or inter-application communication, but there are reasons why a web-service is not an alternative. Another reason is the need for transformation (which is more of a SOA thing than a message queue feature), or if you want or need asynchronous processing.
I my case it was a CMDB application, that generated messages for every change to certain CI types in the database. These messages where then picked up by other systems that needed to be aware of the changes. These systems were used across companies, so poking in each others databases wasn't an option, and webservices would have ment that every database transaction would have to wait for a web service delivery confirmation (a process now handled by the message queue system).
