Windows Azure Messaging Features Come To Windows Server
Microsoft has announced pubic 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.
Service Bus 1.0 has been in beta for some time and is the Windows Server equivalent of the Windows Azure Service Bus. It has features such as Queues, Topics and Subscriptions. It can be configured to be highly available by running in multiple instances and can be durable by saving the messages in a SQL Server database. The programming API of Service Bus 1.0 is consistent with the cloud equivalent and also supports the REST interface. As such, at least theoretically, the same set of code using messaging features can now run in both Windows Azure and Windows Server.
To start developing against Service Bus 1.0, you can go through the walkthrough on MSDN. Also have a look at the CloudFX library that abstract some complex mechanical tasks when dealing with Service Bus, such as implementing a retry logic.
In addition, things like ActiveMQ and RabbitMQ and WMB and ... etc that are not tightly coupled to Windows, just in case you are in a world that is more than just Windows - or would like to depend on more "mature" products.