Use a plastic table cover from the dollar store. This is good for gift baskets, kid's toys, or if you're just plain lazy and/or cheap. All the stuff you don't have a box for, not enough wrapping paper for, or simply don't want to have to buy special boxes or extra rolls of wrapping paper for. That kinda stuff.
Either use it the way you traditionally wrap a gift (hospital corners and all), or plop the gift in the middle and gather up the sides at the top then tie it all the gathered edges together with a ribbon. Or yarn. Or string. Or whatever.
Other tips from Toni Ryan's Fast Cheap Christmas Solutions collection