A lightbox is definetely the way to go. You also need the right kind of lightbulbs in them. They have to give off the right kind of light.
Use lightbulbs similar to these - http://www.greenelectricalsupply.com/day-light-cfl-bulbs.aspx . They have a unit of measurement to measure the kind of light they give off and you want the ones that are daylight bulbs or 5000K, they simulate the light given off by the sun which is best for bringing out the true colour of an object. They will stock them in your local hardware store.
If you really want to go the extra mile you can get someone with photoshop to make the background pure white for you, as in the same colour white that shows up on a computer. I did this for my online craft store and the results are amazing. The images really do look professional. If you cant find someone with photoshop you can check out www.elance.com or www.odesk.com where you can hire someone to do it for you. Shouldn't cost more than a couple of dollars an image.