The Microsoft® Office Information Bridge Framework is a set of software components, tools, and prescriptive guidance that enable developers to create solutions that connect Microsoft Office System applications to virtually any enterprise system or application.

Microsoft Office Information Bridge Framework 1.0 BETA

Microsoft Office IBF SDK beta

Didn't get to try it out yet, since I only run VS.Net 2005 at home, but it looks very cool.

update:

More information is available in the Office Developer Center.