Getting the fleas all out of the house is half the fight. If you live out in the country, long grass can be a haven for fleas. I've found that (where it won't damage your furniture or floors) pine sol seems to work well in cleaning up the house. For clothes, rugs, or other things that you don't want to put pine sol on, putting it through the wash, or setting it sit in the sun for a while (I might add putting it in a black trash bag for good measure) can get the fleas out of that stuff. They sun cooks them, so they run.
I use fresh garlic, chopped up, and give it to my animals once a month to prevent fleas (and worms, and ticks, it's a natural antiparisitic!). Garlic oil, I've heard, works too, but I prefer the fresh chopped stuff. If the animals already have fleas, then you will probably have to give it to them more often (I started using it daily for about 5 days, and after that, just monthly like the normal flea medicines). It might make your animals stink, but as far as I've experienced, that's the only drawback!