Sports Photography
It's an interesting challenge. Dealing with the speed of the action, uncertain lighting, having the right equipment, etc. This is where the D3 excels as its sensor can still see in poor light and its auto white balance largely copes with weird lighting. Not having to be too concerned about the number of shots taken is also a massive win against slides.
Basketball
I've shot both the Australian Mens and Womens National Basketball League from the stands as well as the very occasional NBA game.
Cycling
Mostly the Tour Down Under (and associated races) but also a couple of track events at the Superdome.
Formula One
I think I stopped going to Formula One races before I bought my first DSLR, and so also before autofocus cameras and the photos will be scanned slides. As I've only gone through a small number of boxes don't expect many Formula One photos yet.
Hockey
Not a sport I normally watch but I took my camera down to the Hockey Centre when the Chinese national team was in town and took on the local mens team.