NVIDIA has agreed to make their SLI technology available for AMD 9-series chipset boards supporting Zambezi processors based on the Bulldozer architecture. Only the 990FX and 990X will be supported, so 7 and 8-series board owners are kicked to the curb unfortunately.
AMD 990FX will support 2 x PCIe x16 slots or 4 x PCIe x8 slots, being capable of 2-way (dual x16) or 3-way (tri x8) while 990X is only capable of 2-way (dual x8). At the moment there is no news of the AMD 970 being capable of SLI.
The AMD 9-series is expected to launch in May.