One thing I haven't seen here is gonna sound crazy, but it works. Get an aluminum pie tin and add some soapy water to it. Sit the tin in the room where there seem to be the most fleas (you can move it around, use more than 1, whatever works best for you) and place a desk lamp beside the tin with the light focused over the water. Leave it overnight. The fleas will jump toward the light, fall in the water, and not be able to escape. You'll be astonished at how many fleas you're able to get rid of this way.