The 300mm f/2.8 IS is one of Nikon's best lenses.  It's not too heavy, and the Vibration Reduction system delivers 3 stops of anti-shake compensation, so it's very popular with sports photographers.  It can be used hand-held, but a tripod or monopod is recommended.

This lens works very well with Nikon Teleconverters and it will still deliver superb image quality.  The 1.4x Teleconverter makes it a 420mm f/4 lens; the 1.7x Teleconverter makes it a 510mm f/5-ish lens; and the 2x Teleconverter makes it a 600mm f/5.6 lens.  All of these combinations will retain autofocus and VR on all compatible cameras.

Suggested extra: You might find the Manfrotto MN393 long lens bracket useful when mounting this lens on a monopod or tripod.