Nikon recently announced that it will release two new dSLR cameras in order to compete with Canon's newly announced 40D and 1Ds Mark III.

Full final specifications are not yet out, but the main things are as follows:

D300
Body material - Magnesium alloy
Sensor
• 23.6 x 15.8 mm CMOS sensor
• DX format
• RGB Color Filter Array
• Built-in fixed low-pass filter (with self-cleaning unit)
• 13.1 million total pixels
• 12.3 million effective pixels
• 3:2 aspect ratio
Image processor - Nikon EXPEED
A/D conversion - 14 bit
Usable lenses
• DX AF NIKKOR: All functions possible
• D-/G-type AF NIKKOR (excluding IX NIKKOR lenses): All functions possible (excluding PC Micro- NIKKOR)
• AF NIKKOR other than D-/G-type (excluding lenses for F3AF): All functions except 3D-Color Matrix Metering II possible
• AI-P NIKKOR: All functions except Autofocus, 3D-Color Matrix Metering II possible
• Non-CPU AI NIKKOR: Can be used in exposure modes A and M; electronic range finder can be used if maximum aperture is f/5.6 or faster; Color Matrix Metering and aperture value display supported if user provides lens data
Auto Focus
• 51 focus points (15 cross-type sensors) *
• Multi-CAM 3500DX *
• AF working range: -1 to +19 EV (ISO 100, normal temperature)
• Contrast Detect in Live View (Tripod) mode

It also features a HUGE LCD screen (922,000 pixels), live view with auto-focus, HDMI output, UDMA support for CF and a lot of other goodies. Find more at DPReview.

D3
• First ever Nikon DSLR with a Full-Frame (36 x 24 mm) sensor (coined FX format)
• 12.1 megapixel full-frame sensor (8.45µm pixel pitch)
• ISO 200 - 6400 (with boost up to ISO 25,600)
• Also supports DX lenses, viewfinder automatically masks (5.1 megapixels with DX lens)
• 5:4 ratio crop mode (10 megapixels, up to 9 fps, viewfinder masked)
• 14-bit A/D conversion, 12 channel readout
• Nikon EXPEED image processor (Capture NX processing and NR algorithms, lower power)
• Super fast operation (power-up 12 ms, shutter lag 41 ms, black-out 74 ms)
• New Kevlar / carbon fibre composite shutter with 300,000 exposure durability
• New Multi-CAM3500FX Auto Focus sensor (51-point, 15 cross-type, more vertical coverage)
• Auto-focus tracking by color (using information from 1005-pixel AE sensor)
• Auto-focus calibration (fine-tuning) now available (fixed body or up to 20 separate lens settings)
• Scene Recognition System (uses AE sensor, AF sensor)
• Picture Control image parameter presets (replace Color Modes I, II and III)
• Custom image parameters now support brightness as well as contrast
• Nine frames per second continuous with auto-focus tracking
• Eleven frames per second continuous without auto-focus tracking
• Ten / eleven frames per second continuous in DX-crop mode (AF / no-AF)
• Dual Compact Flash card slots (overflow, back-up, RAW on 1 / JPEG on 2, copy)
• Compact Flash UDMA support
• 3.0" 922,000 pixel LCD monitor
• Live View with either phase detect (mirror up/down) or contrast detect Auto Focus
• Virtual horizon indicates if camera is level (like an aircraft cockpit display)
• HDMI HD video output
• 'Active D-Lighting' (adjusts metering as well as applying D-Lighting curve)
• Detailed 'Control Panel' type display on LCD monitor, changes color in darkness
• New MB-D10 vertical grip fully integrates into body, multi battery type compatible
• Buttons sealed against moisture
• Dual battery charger as standard
• Available November 2007

Source: DPreview