I finally set aside a little spare time to make myself a light box for taking my jewelry photos, and I'm really glad I did!
I just got a sheet of white foamcore board, and cut it into ten inch squares and taped them together to form a little cube, with one side open. I also bought a daylight spectrum light bulb to shine into the box. The box bounces the light around so you get a nice even light over your piece, without the glare you would get from lighting a piece of jewelry directly. I just set the white balance on my camera to the inside of the box and took my pictures. I didn't need to do any color adjustments or anything. I'm still by no means a professional photographer, of course, but I feel like I'm getting some good photo quality from my little lightbox.
The best part is that now I have consistent lighting for photos any time of day, I don't have to worry about how the weather will affect my photos, or try to get my pictures taken before the sun goes down (at 5 pm here in the winter!)