I have read that if you take viniger and schreaded steelwool and put it in a container for a week or so it forms a brown solution that will ebonise wood. I am also told that woods like walnut work best. I have never tried it but thats what I've been told..
Corey, I have used the steel wool and vinegar thing, I have used stove or lamp black, and I have used Rustoleum! A thinned coat of Rustoleum or other black paint can go a long way to ebonizing, and if you want it really black, don't thin the paint!