The Nikon SB-800 is a great flash. I'm a big fan of the Nikon Creative Lighting System. The SB-800 usually runs around $350. To get the most out of the newest Nikon technology, you need to use the SB-800 as your master flash. The SB-600 runs under $200 and can be used as fill flash when controlled by the 800. You really need to get the master flash off of the camera shoe. The older SC-17 cable, or the newer SC-28 will get the master flash away from the camera and then there are longer cables and remote shoes for fill, rim or back light flash units. The whole deal could come in under a $1,000. You'll want some light stands, adapters, and sand bags too. The diffuser shown in Chuck's picture is the LumiQuest.

Best,
David