Diatomaceous Earth

DE is a powder made from crushed fossilized diatoms (hard shelled algae). It makes an awesome all around pest control. It can be used

-in gardens
-around the exterior of the house/windows
-as an instant bug killer (great for spiders, ants, roaches)
-fire ant hills
-yellow jacket nests
-treating carpet for fleas
-directly on dogs and cats as a flea killer and prevention
-just about any other time you need to kill an invasive critter

DE is very safe. It can dry your skin if you handle it frequently, and it's best not to snort it. :) It's even edible. Most flour and baking mixes (like Bisquick) contain DE to kill any sort of bugs that might get in it. Chances are, you've eaten DE.

You can buy DE in garden stores. Just make sure you get FOOD GRADE DE. There is another version sold for pools that is highly toxic.

(Thanks dobie_mama, for turning me on to DE :))