Originally posted by Tony3d I am very interested in doing product photography.
What will you do with your product photos? How will they be viewed? Will they be printed in catalogs, shown on websites, printed as posters, be used to sell stuff on eBay, or what? Will they be greatly enlarged? In other words, what resolution do you need? And how tiny are the products you'll be shooting?
The 18-55 kit lens focuses to about 4 inches. That's pretty close. With an inexpensive close-up or 'diopter' lens attached, you can go even closer and get magnification, as johnmflores shows. A powerful closeup adapter like a Raynox DCR-150 or -250, not very expensive, gets you closer yet. You really only need a macro lens if you wish to fill the frame with something that's around 16x24mm (2/3 x 1 inch). And to work at that level, with your light cube and non-flash lights, you can get a manual lens and macro extension tubes for much less than a macro lens.
I asked about resolution because I shoot (sometimes small, 1x1 inch) objects to sell on eBay. I almost always use my old Sony DSC-V1 P&S camera, 5 mpx, focusing to 4 inches, inside a 15 inch light cube. I still need to shrink the 2592x1944 images considerably for screen display. I find the small camera is much easier to use than my K20D (with or without macro setup) for this purpose. And its included charger lets me keep the camera line-powered for long sessions, without worrying about draining batteries.
There's a book, EBAY PHOTOGRAPHY THE SMART WAY (which you might find online as a PDF) that covers just what you need to do to be effective. Have you read anything about product photography?