I have a Sony A900 that I want to use with Nikkor AF-S 70-300mm f/4.5-5.6 G IF-ED VR. Does this lens come with a Sony mount? I do not want to have to use an adapter.
No. In general, Nikon make lenses only for Nikon cameras. I'm sure there are one or two exceptions out there, but this isn't one of them.
If you cant get it fit on your camera you always have an adapter to aid the mounts of the lens