I'm not a pro or anything, but I think I can help a little...
It depends a lot on the size of the product you're photographing. I take a lot of 'product photography' type pictures of my stuff so I have a picture of it if it ever gets stolen or something.
For small objects (like the size of a baseball or smaller) I usually use my 100mm Macro. For larger things I use either my 50mm 1.4 or 85mm 1.8.
With a tripod and good lighting you could probably use just about any lens.
I do product photography for several different companies. I find myself using my [FONT=Verdana,Arial,Helvetica,sans-serif]Canon EF 100mm f/2.8 Macro[/FONT] and my[FONT=Verdana,Arial,Helvetica,sans-serif] Canon EF-S 17-55 f/2.8 IS most of the time. Here are a few examples. First two were shot with my 100mm Macro and second two were shot with my 17-55.
I would imagine that a 100mm Macro would be ideal for most hand-sized objects. For product photography, focusing out to 1 meter would work very well with that kind of lens.
I personally use my 50mm at high fstops because it's still reasonably sharp there, but also because I don't have a good-quality 100+mm alternative. My Sigma 70-300 isn't really that great.