I’ve just released a small tool on CodePlex that lets you convert from a TeX bibliography (such as that done in JabRef) into an XML file that can be read with Word 2007. It’s called bib2Word07Xml and you can get it from http://www.codeplex.com/bib2Word07Xml, under the Releases tab. There are some limitations, these are documented on the project homepage. Please feel free to leave any comments on the project pages.
You can read the outputted XML file into Word 2007 by clicking References->Manage Sources->Browse, and selecting the XML file. To use the references and cite as you write you simply copy the references you need from the Master List into the Current List, which allows you to Insert Citation where you need to in your document.
The only pre-requisites are the .NET framework 2.0 or above on Windows machines or the latest version of Mono on Linux machines. Enjoy!