Well... I purchased an inexpensive Nikon lens to Sony A mount adapter from Ebay and am having good results so far with the 35mm Distagon T* 2/35 lens. The 25mm Distagon T* is okay... but not as good as the 35mm.
My trials so far are showing Vignetting with the Zeiss 100 Makro and the 50mm Makro. Haven't tried the 85mm yet but will soon.
So far I've just been able to focus in the viewfinder with no Focus indicator... but I have another adapter coming that will give me that option. The lenses meter just fine though.... although I have no F stop readout... so I have no idea what aperture I shot at except from memory
Here's a few test shots from a walk around yesterday with the 35mm and adapter on the A900: