Version 4.0 of NServiceBus, a service bus for .NET, has just been released with support for RabbitMQ and ActiveMQ in addition to MSMQ. Support for using database tables as queues has also been added, and performance for the MSMQ transport has been significantly improved. According to Udi Dahan, the founder of NServiceBus, this is the biggest release ever.
The recently released Windows Azure Service Bus Client SDK provides support for task based versions of all asynchronous APIs in addition to performance improvements.
Microsoft has announced public availability of Service Bus 1.0, and it will be free to use with a properly licensed Windows Server. This makes features from Windows Azure Messaging available on in-house infrastructure.
For quite some time now BizTalk has been essentially on life support. Being both very complex and very expensive, it was never a particularly popular product. None the less, many companies used it because they trust the Microsoft name and actually do need some sort of enterprise service bus. Seeing this gap, Microsoft has created a new product called Microsoft Service Bus 1.0 for Windows Server.