A forum member
at OCWorkbench claims that he's created a version of the 84.29 driver that enables you to run SLI on Intel an ATI chipsets.
However, there are some restricitions, as it doesn't works with any of the new 8x00 series of cards and it won't work with the 7950GX2.
There's no proof posted, just a pictured of a DFI board with an ATI chipset with two Nvidia cards attached to it. Furthermore, the drivers are password protected, but the forum member said he would post the password in seven days after the original post.
It sure sounds dodgy to us and we very much doubt that this really works. Reportedly there are some limitations and some texture issues in some games as well.
You can read the forum post here