Some great non-chemical flea controlers are food grade diatamaceous earth (DE) and Borax(20 mule team brand).
The DE is sprinkled and brushed into the carpets,difficult to vaccum places,dog bedding, under furniture, under couch cushions and crevices as well. A food grade DE should be used and not the pool supply kind. Here is a where I get mine from, great customer service and fast shipping--
http://www.wolfcreekranch.net/defaq.htm
Borax found in the laundry section of most stores and goes by 20 mule team brand is great for outdoor appilcations. I put mine in an old large size spice bottle that allows me to sprinkle it throughout the yard. The Borax can also be used indoors if your flea problem is really bad. It should be used the same way as the DE. I have found the Borax to be extremely effective in the yard.
I have had limited success with the ACV spray, but did find a lemon tonic to be more effective or an Essential oil mix consisting of lemon and other oils to work well. The lemon tonic or essential oil can be toxic to your cats if it is sprayed on them or they lick the dogs.
Lemon tonic recipe -- One lemon washed and thinly sliced added to 16oz. water. Bring water to a boil and remove from heat. Let steep for at least 8hrs or overnight.
My personal addition to this recipe is fresh rosemary 2cups, sage 1cup and Lavender 1cup. These are not necesary, but I grow them and they are know for bug reppeling qualities. After steeping I pour this mixture into a a spray bottle and squeeze as much liquid out of the lemon herb mixture. Store in the refigerator. This is sprayed on the dogs when we go on walks where fleas are prevelent. This spay is also supposed to work for tick. If fleas are not very prevelent I may do an application about every 3-4 days. Water will remove either of these spays.
For the essential oil mixture I use a premade oil from Smith and Hawkins garden store called Bug Off. I add one drop per ounce of water. In addition you can add Neem oil or tea tree oil(one drop per 2oz. of water). The addition of a natural castile soap, about a table spoon per 30 oz. will help with the oil and water mixing.
The application for both is just shake and spray being sure to get the coat and skin. It can also be sponged on. Use caution around the head and face. I use these sprays on myself as I found sometime when we came back from a trail run I would have fleas myself.
These methods are not sure proof, but I have found them very effective. Since my dogs have short hair I do a quick body check for fleas and ticks when we get home from a walk or hike, occasionally I may find one flea,where as before the spray I could easily find 4-5 everytime. Vaccuming carpets is a critical to keep fleas out of your home as well.