Nikon's D60 is the successor to the D40x, and virtually identical to this model. It shares the same 10.2 Megapixel sensor, the same screen, and virtually the same body. New to the D60 are a stop-motion recording mode, eye sensors which switch the screen off, Active D-Lighting, an anti-dust system and an optional kit lens with VR stabilisation. Like the D40x though, you'll still need AF-S lenses to autofocus.
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Nikon’s D300 is the successor to the popular D200 and features a self-cleaning 12.3 Megapixel sensor, 6 fps continuous shooting, an HDMI port, and a high resolution 3in VGA screen with Live View capabilities. There’s a new 51-point AF system, 14-bit A-D conversion and a scene recognition system, along with shutter speeds from 30 seconds to 1/8000 and sensitivity from 100 to 6400 ISO. With tough build and many of the D3’s features, the D300’s an affordable pro DSLR.
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The Nikon D3 is the company’s new flagship DSLR and its first with a full-frame sensor. This 12.1 Megapixel sensor allows lenses to operate without a field reduction, but retains compatibility with DX format optics by only using a cropped area of the sensor. The D3 also boasts 9 fps continuous shooting, a new 51-point AF system, 14-bit A-D conversion, an HDMI port, and a high resolution 3in VGA screen with Live View capabilities.

The D40x is a 10.2 Megapixel version of the entry-level D40 DSLR, see below. The higher resolution sensor brings additional benefits including slightly quicker 3fps shooting and sensitivity which starts at 100 ISO, but otherwise it’s the same camera. Like its predecessor, there’s a 2.5in screen with easy to use menus and a basic 3-point AF system. It remains ideal for first-time DSLR buyers.
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The D40 is Nikon’s new entry-level DSLR and successor to the D50. It features the same 6 Megapixel resolution as the D50 but upgrades the screen to 2.5in and features an improved version of the kit lens. The AF is a basic 3-point system and the D40 will only provide auto focus with modern AF-S lenses, but it will appeal to those wanting to get into DSLR photography at a low price point.
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Nikon’s D80 is the successor to the popular D70s, featuring the D200’s 10.2 Megapixel resolution in a more affordable, mid-range body. Improvements over the D70s beyond the sensor include a 2.5in screen, refined 11-area AF system, 3200 ISO sensitivity, 3 fps continuous shooting with a 100 JPEG buffer, support for SD(HC) memory cards and an almost instant 0.18 second startup time.
More info at Camera Labs: full review