RabbitMQ itself doesn't have HA built-in, but warm spare HA is rather simple and well-documented, built on-top of Pacemaker and DRBD. It works quite well.
The docs for HA are here: http://www.rabbitmq.com/pacemaker.html
This also works with Veritas if you use that instead of DRDB.
Please note that we are currently QAing a new HA model which is active/active. Watch this space!