I really like DE for indoor use as well. Not only is it 'inorganic' but it is an inert substance that kills the bugs mechanically, not by chemically poisoning them. Don't use it outdoors, except maybe for slugs and snails (on the ground) as it will also kill beneficial insects like bees and ladybugs. Also wear a mask if you use more than a little big, as it can irritate your nasal passages - makes me sneeze! I buy the garden grade, although not as 'pure' as food grade DE, it is still very safe.
Here's a (ridiculously long) link that explains it:
http://organicgardening.about....
