The Nikon 70-300mm f4.5-5.6 VR is definitely the best bang for the buck. I have one, Osmosis has one, Kirbinster has one...
There is a nice review here:
Nikkor 70-300mm VR tested with Nikon D80 full review Cameralabs introduction
The 70-200mm f/2.8 is too expensinve IMO (that's me) for what I'm doing. If I want to shoot sport, I just make sure it's during daylight.