In this driver commit, it's exposed that the IGDNG desktop device is Clarkdale and the mobile version of IGDNG is Arrandale. This actually makes it even more interesting since Clarkdale and Arrandale are (32nm Core i3 and Core i5) CPUs but with an integrated GPU supporting switchable graphics.
Clarkdale and Arrandale aren't expected to appear in the consumer market until the late part of Q4 or very early 2010, by which time the open-source graphics developers at Intel will have been working on this support for more than six months. IGDNG support is also appearing in the DRM with the Linux 2.6.31 kernel, so there should actually be "out of the box" support for these GPU-on-CPU parts by the time they arrive.
Kudos to Intel in having their open-source Linux developers begin working on the Clarkdale and Arrandale support in the public spotlight so early.