Another vote for mineral salts (aka. deodorant crystal). The spray is easier IMO. I think people have been using it for a couple thousand years. And it doesn't stain your shirt pits like most deodorants do.
where do I get mineral salt spray?
Amazon, Whole Foods, drug stores, health food stores, etc. The spray is just mineral salts dissolved in water. Do a google search for "crystal deodorant spray" and you'll find a gazillion places to buy it.