For product stills, I'd get a D3100 with the new 40mm F/2.8 macro lens, a flash, tripod, and a cheap light tent.
The flash and light tent will ensure proper lighting on your products, the tripod will prevent you from going crazy because you don't have enough arms to hold everything, and the macro lens will ensure you can also photograph any smaller products you might have.
The D3100 has what's called CLS, Nikon's wireless flash system. If you buy one of their flashes (SB-600, 700, 800 or 900), you can position the flash remotely; it does not have to be on your camera. It will make your life a lot easier if you're trying to light your products
The D3100 also has "Live view", meaning you can see what the camera sees on it's rear screen. It makes for easier focusing, and saves your back when you're working with a tripod (you don't have to lean in to the viewfinder).
For general photography, I'd toss in an 18-55 VR lens or, if budget allows it, an 18-105 VR lens for more reach.