Alex Woodie walks us through some of the options available for message buses:
Apache Kafka
Apache Kafka is a distributed open source messaging bus that was written in Java and Scala. The software implements a publish and subscribe messaging system that’s capable of moving large amounts of event data from sources to sinks, in a high-throughput manner with minimal latency and strong consistency guarantees. The software relies on Apache Zookeeper for management of the underlying cluster.
Kafka is based on the concept of producers and consumers. Event data originating from producers is stored timestamped partitions that are housed within Kafka topics. Meanwhile, consumer processes can read the data stored in Kafka partitions. Kafka automatically replicates partitions across multiple brokers (or nodes in the cluster), which allows Kafka to scale its message streaming service in a fault-tolerant manner.
Click through for descriptions of several good options. And if you want a big list, queues.io has one for you.