If you have a little time, one of the best things you can do is drill some holes, about 3 - 6 inches deep, and fill the holes with saltpeter. There are products out there such as Stump Away, but all they are is saltpeter (my understanding). The stumps will rot in about 6 months, then you can fill the holes with diesel fuel and light them on fire. They won't actually flame, but will smolder until the stump is gone.
Randy