What tubes do I need with a 26X1.5 tire?

should have a range on the box. The tubes I use say 26X 1.9/2.2 and i use them for 26X2.1

The box usually gives a size range, but the size is not all that critical. If the tube is a lot fatter than the tyre, it may be tricky to stuff it into the tyre. I always put in a tube that has some air in it: just enough to stay round.