We have used several of these methods and haven't had a flea on our dog or 16 cats-ever!

Borax/Baking Soda inside

DE outside

Here is a link that might be useful: Natural Flea Prevention

I wouldn't use Borax. Food-grade DE is safe for indoors and outdoors and there's no risk of it harming the dogs if it gets in their water bowls or if you or your children breathe it in or accidentally ingest it.
Just coat your yard in Food-grade DE powder. Then lay a paper-thin layer of it on our carpet, vacuum, and then sprinkle another thin layer over the carpet. Apply it liberally in nooks and crannies where the vacuum can't reach regularly. If you have a really bad infestation, you'll need to flea comb your dogs at least twice a week outside or into warm, soapy water.
Hope this helps!
Check out the link below for some great info.

Here is a link that might be useful: Paul Wheaton articles on permaculture - flea control

monkeys???

yep monkeys lol,thats an idea get a monkey to pick & eat fleas off your dogs.