I found some excellent resources for Jewelry or still photography. Ranging from items which are purchasable to items which you can build.
One of the keys to taking great Jewelry photographs which can be cropped or used on a web page is to have evenly distributed lighting. That means that there are no shadows, and that the object is illuminated from all angles. The way to do this is by means of defused lighting.
One excellent solution for creating diffused lighting is by means of something called an "EZCube". This is a light weight fold-able cube, within which you place your object. On the outside of the cube you put several light sources. The parachute type canvas of the cube diffuses the light from the lamps, and distributes it evenly within the cube. This creates a optimum environment for a great picture.
Example of an EZ-Cube:
These type of cubes can get a bit expensive however. The EZCubes themselves run from $60-$120. However you will also need some fairly descent pure white sources of light. The entire kit can run upwards of $300-$400. You can find cheaper version on EBay though.
The official source for the EZCube is:
EZ-Cube Web Site
That having been said, there are some cheaper alternatives. In browsing the web, I found one site where someone created some excellent instructions for building one yourself from PVC pipe, and some materials. My thanks to Bill Huber for creating this excellent site:
How to build a Photo tent
Hope some of this information helps! Good luck and happy snapping!
www.pbase.com/wlhuber/light_box_light_tent