Yes. All modern Nikon bodies use the same lens mount. The only thing is that if any of your lenses are "DX" then that means they’re only designed to project an image circle onto the smaller sensors found in cameras like the D90 and D300. They’ll still work with the D700 and D3, though the picture will be auto cropped to only use a portion of their much larger FX sensors equaling roughly 5 Megapixels.

The benefit of full frame is that you’re getting a sensor that’s actually the same size as a frame of 135 film. This means there’s no crop factor… lenses that were designed for standard 135 film cameras will have the same field of view. Also the much larger surface area means that they can collect more light, which leads to improved ISO performance and dynamic range.
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"The benefit of full frame is that you’re getting a sensor that’s actually the same size as a frame of 135 film"

can anyone explain me where the advantage is. A 100 mm lens is a 100 mm on any camera, even on a DX sized sensor. Only thing is that the DX sensor, being smaller will just show a cropped part of that shot, same as if you take the 100 mm full size sensor shot and go to any photo-editor and cut out the center part of it to half the size.

Advantage on DX is the wider field deepth. On FX or full sized sensor the DOF gets so close that on a party or inside a room with many people it gets just impossible to get all people more or less sharp.
On a DX sized APSC sensor, that field deepth is much wider and the chances to get a sharp all over shot is more evident. So, see that a full sized sensor has not only advantages. On a DX you can do same un-sharpness with playing lenses and apertures, on an FX full sized you can’t get what the sensor doesn’t allows you.
The believings that a full frame sensor is the top or must is another digital religion anyway. A D3/700 shoots larger pictures with same resolution as a D40, A D3x shoots in same resolution and double size pictures as a D200. So, is there any bargain there …. ?
Now, just any lens from Nikon works on a D300/700/90. As one said, on full sized sensors, the camera will recognize the lens and reduce the sensor coverage to the crop factor the lens covers, and on D3/700 its 5.1 mpix on D3X it’s 10.5 mpix. So expect a D3/700 to shoot in D2H quality and size and a D3X in D200 quality and size when using a DX lens.

Note that for the price of a D90 you can buy a D200 or Fuji S5 Pro body. They are cheeper and better, just they do not have all that tech crap you don’t need anyway. The Fuji S5 Pro is unbeaten when it comes to color dynamic and here the new Sony A900 and D3x with same chip are not even close to it. In dslr’s, more pixels (beyond 10 mpix on an apsc) just brings more noise and what makes cameras progress is the software cheats only and reducing or flattening excessive noise is a better way to destroy a picture. Have you ever seen any former film camera delivering good shots at more then 400 asa. Note that a Fuji S5 shoots clean up to 1250 and "please" without any disturbing and noise flattening at all. It’s the only camera i ever had in my hand that was able to do that.
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