For sports photography, APS-C digital SLR has the advantage of longer reach with the crop factor.  For Nikon,  the crop factor is 1.5.  Since Nikon lenses are very expensive especially the long telephoto lenses, the extra reach with the APS-C  Nikon digital SLR will offset the lens cost somewhat.

The best Nikon APS-C digital SLR for sports photography is Nikon D300.  Nikon D300 is better than Canon 40D for sports photography-but at a deeper price.

• Nikon D300 is the fastest Nikon APS-C digital SLR with the continuous shooting speed of  6 fps (or up to 8 fps with the optional Multi-Power Battery Pack MB-D10 attached.

• Nikon has max shutter speed of 1/8000 

• Nikon D300 has excellent  auto-focus module (Multi-CAM3500DX) that delivers fast and accurate AF lock 

An excellent ports lens for Nikon D300 is Nikon 70-200mm f/2.8G ED-IF AF-S VR ($1706).  More affordable Sigma 70-200mm f/2.8 DG HSM II Macro Zoom Lens ($699), or Tamron AF 70-200mm f/2.8 Di LD IF Macro Lens ($639) are also good.

Buy Nikon D300 on amazon:

Nikon D300 DX 12.3MP Digital SLR Camera (Body Only)