Miguel, I'm with you: a salt crystal makes the most sense. Using a sticky, perfumy anti-perspirant or deodorant to block up pores or cover up odor just doesn't make any sense, because sweating is a natural function for thermoregulation. A salt crystal does neither. What it does is change the ph of the environment so that bacteria don't proliferate so rapidly. Some people's ph is such that they can accomplish this whthout doing anything other than regular bathing, and some people can't. Humm, maybe ph has something to do with diet. Anyway, the bottom line is regular hygene, and while on the trail I wash up every day with just water.
Kevin made a good point about using wool: it does not stink! Sarah, I threw away all my synthetic t-shirts and now use only the lightest Smartwool t-shirts. Talk about a difference! They're odor free even after a week and are comfortable both in summer and winter. If you stink after only a couple hours, you need to get some (merino) wool. Trust me on this and you'll never go back to petrochemical fabrics. Happy trails.