There's a minor issue with doing this comparison online: the color profiles of all three photos are different. The first is Adobe RGB, 2nd is Nikon Adobe RGB (Nikon's version of Adobe RGB) and the last is sRGB.
Only the last image has the correct profile for the web, which is sRGB and for this to be a better comparison all images should've been posted with that profile.
This is important because not all browsers currently interpret images correctly based on the embedded profiles and most assume that all images are in the sRGB profile. This could lead to images using Adobe RGB (and other profiles other than sRGB) to be show incorrectly by browsers compared to what you might see in an application that properly manages color spaces, such as Photoshop, Capture NX, Aperture, Lightroom, etc.
In this case, not only are the images different due to the the raw rendering of all the applications, but also due to the incorrect rendering of your particular browser and the platform you are on (gamma difference between Mac and PC).
For example, some people mentioned that B looks too saturated, especially in the yellow shirt. It looks like that too me as well using Safari on the Mac, but in Photoshop the Nikon Adobe RGB (same as regular Adobe RGB) color profile displays it less saturated and the yellow is more mellow.
Anyway, just something to keep in mind. For best result, save all images for the web using (or convert to) the sRGB color profile.
Personally, I prefer the Aperture version. I find that it renders the most neutral image with the most realistic colors with decent contrast and corresponds to the Neutral Picture Control of the D300. Then again, Aperture is my main photo application so I could be a bit biased.
Also, Capture NX is the only application out of the three that can read the internal Picture Controls in the D300, so B is probably closest to what you saw on the camera LCD. From the looks of it, the camera was set to Standard which creates rich images, maybe a bit too saturated, with skin tones that are a bit too "gummy" and smooth for my taste.