To kill fleas in the house without chemicals (and cheaply!!!), try this:
http://www.thriftyfun.com/tf747531.tip.html
It WORKS!!! (although I leave it on for a day or a weekend if I can, before vacuuming!)
We've used salt as well. (We have a lot of animals, and live in a flea-heavy area, and esp. when my babies were crawling, I was worried about chemicals.)
For a really bad infestation, while doing the above, set pie pans full of water (with a drop of liquid dish soap) on the floor in front of a light source at night. The fleas jump towards the light, into the water (the soap breaks the surface of the water) and they drown.