I've discussed the MA0C SupportPac, one of the WebSphere messaging product options for using WebSphere MQ to perform publish/subscribe messaging. It turns out there's also the MA0D SupportPac: Getting started with MQSeries Publish/Subscribe. It explains pub/sub in general and discussed how to use the MA0C pub/sub broker in WMQ. So if you're going to use MA0C, you should check out MA0D as well.
JMS: MA0D: Getting started with MQSeries Publish/Subscribe