I second (or third) the garlic suggestion. Chico gets two garlic & brewers yeast doggie tablets a day.
For the yard, it's been suggested that we use diatomaceous earth (not the pool filter kind, though, which has been treated). It's non-toxic (though the dust could irritate your lungs, so use a dust mask and keep your dog inside until it settles, or apply it wet so it isn't airborne) and kills crawling insects mechanically, which is a WHOLE LOT better than spraying poison on your lawn. It also means fleas can't develop an immunity to it, like some poisons. You can use it in the house, too. Read more here: http://www.commonsensecare.com/content/msds-de.doc