Is the house is both one story and has an unfinished basement or crawlspace, it's not that hard to change the wiring for the outlets and get them grounded. An electrician will probably drive a copper pole into the ground somewhere outside to ground everything to, and then run new wires to the outlets. Because outlets are generally low to the ground, rewiring them if you can get access from the floor below is pretty easy.
Or you could do what a previous owner of one of our houses did. They grounded a lot of the outlets to the water pipes. The pipes are grounded because they go into the ground, but it does make them corrode a lot faster apparently. I'm pretty sure this is not considered an ideal solution, but the inspector when we bought the house, the insurance inspector, and an electrician all seemed pretty blase about it. None of them were alarmed and said it was awful, so we lived with it for years like that.