Updated version of example from Andrey Paramonov's blog post - http://ndpar.blogspot.com/2010/03/get-started-with-rabbitmq.html

consumer.groovy

import com.rabbitmq.client.*

@Grab(group='com.rabbitmq', module='amqp-client', version='2.8.7')
factory = new ConnectionFactory([username: 'guest', password: 'guest',
                                 virtualHost: '/', requestedHeartbeat: 0])
conn = factory.newConnection(new Address('localhost', 5672))
channel = conn.createChannel()

exchangeName = 'myExchange'
queueName = 'myQueue'

channel.exchangeDeclare exchangeName, 'direct'
channel.queueDeclare(queueName, false, true, true, [:])
channel.queueBind queueName, exchangeName, 'myRoutingKey'

def consumer = new QueueingConsumer(channel)
channel.basicConsume queueName, false, consumer

while (true) {
  delivery = consumer.nextDelivery()
  println "Received message: ${new String(delivery.body)}"
  channel.basicAck delivery.envelope.deliveryTag, false
}
channel.close()
conn.close()

publisher.groovy

import com.rabbitmq.client.*

@Grab(group='com.rabbitmq', module='amqp-client', version='2.8.7')
factory = new ConnectionFactory([username: 'guest', password: 'guest',
                                 virtualHost: '/', requestedHeartbeat: 0])
conn = factory.newConnection(new Address('localhost', 5672))
channel = conn.createChannel()

channel.basicPublish 'myExchange', 'myRoutingKey', null, "Hello, world!".bytes

channel.close()
conn.close()