Any AM2 motherboard is compatible, but it probably needs a bios flash as Phenom wasn't out when it was released. Even flashing a bios for Phenom support, you'll still be limited to HT 2.0 instead of 3.0. Just check the manufacturer's site for supported processors to see which board and bios revisions support Phenom.
The only Nvidia AM2+ board I saw at Newegg was a single slot 560:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813138081
Keep in mind that Nvidia's supposed to be releasing their new Phenom support boards, both SLI and hybrid SLI in December or January. So you might want to wait a few weeks.
What intrigues me about both hybrid SLI and hybrid Crossfire is that the DX10 IGP's finally work alongside the single discrete graphics card. They improve performance in 3D apps and games, while powering down the graphics card and relying upon the IGP when not needed. Can't wait to see a comparison. It will finally make integrated graphics worth something beyond additional monitor support.