Pancetta, the Italian version of bacon, is made by seasoning a pork belly side with salt and lots of pepper, curling it into a tight roll, and wrapping it in a casing to hold the shape. It differs from bacon in that it is cured, but it isn't smoked.
You can substitute bacon (though it will add a smoky flavor, too). To lessen the smokiness, blanch the bacon before using it.
Pancetta used to be sold only at Italian markets, but it's now available at most supermarkets, usually sliced to order at the deli.
Pancetta should be cooked before eating. It is often sold sliced to order. For easier chopping and dicing, freeze it briefly and use a sharp knife.
Keep pancetta refrigerated where it will last for a few weeks. Unused pancetta freezes well; wrap a few slices together in individual packets so it's easy to thaw only the amount you need.