This just in.... Microsoft has just released a Community Technology Preview (CTP) of BizTalk Services, a set of hosted services delivered via the Internet to help developers rapidly build and run composite applications at internet scale.  At it's core, it is an Internet Service Bus.

With platform technologies including Windows Server, the .NET Framework, BizTalk Server, and other so on, Microsoft has long been dedicated to delivering ever-broader application platform value to businesses that want to be able to buy+build+integrate their systems. The “BizTalk Services” ISB extends and complements the existing Microsoft platform to further advance the capability and productivity available to those businesses.

"BizTalk Services” is easily programmed through the familiar .NET Framework v3.0 and Visual Studio. In addition, the “BizTalk Services” capability is accessible through standard Internet and WS-* protocols making them fully interoperable with existing IT investments, and easy to use from a wide range of platforms.

Dino sez, check it out.

Oh, also, some other blogging attention: 

eWeek did a story, too