Azure Service Bus is part of Windows Azure AppFabric. AppFabric has received much less press than the Azure hosting, storage & SQL Azure. Maybe because it targets more advanced scenario, maybe because it’s confusing everyone because of its name baring a striking resemblance with Windows Server AppFabric, who knows?
Nevertheless, Azure Service Bus has a very powerful architecture allowing parties behind different NATs or firewalls to communicate with each others. It also allows multicasting information, in a publish-subscribe manner. This last feature interests me a lot and I’m sure I’ll be blogging about it again and again!