I use it around the foundation of our house to discourage creepy crawlies, and inside the house in all those "dark corners" and on animal beds when we have flea troubles as we did this past year. (We still had to use Advantage on the animals, but I think it helped to keep the fleas from re-populating.) It is great for killing caterpillars before they denude your garden plants, which reminds me I have to dust my orange azalea...
As others have said, make sure you get the agricultural (not pool) type, and also wear a mask if you're spreading it around. It's a very fine powder, not toxic but probably not good to breathe in anyway.
I've read online about using it for a wormer, but haven't tried it myself on our animals.