ive never found one to work, i had a hippy female freind that used a 'crystal' something or other, and that didnt work, then she read that the reason sweat smells is because of the toxins in your body, once you sweat them out your armpits will stop smelling (works for the middle easterners right?) and that didnt work at all. so no, they dont work.
Pretty much ditto this post for me, except I have to trim my armpit hair because the damn crystal twizzles me hairs into painful knots. A trick to improving the performance of the crystals is to get the spray version as well. I spray on the spray instead of wetting my pits with water, then I rub in the crystal.
Word of warning: don't drop the crystal, it will explode into about 90 trillion bizillion pieces. I've dropped two so far.
Make sure you're washing your pits like nuts, otherwise you're dicking yourself up. Large lymph nodes use the area so make your life better by cleaning up what they put out. I steer clear of antiperspirants because I'd call it a bad idea to block the largest detox organ in the body, but what do I know.
On the issue of natty DO's, Tom's of Maine for skizz if you're into that. I just use basic RightGuard deoderant sand the anti... works wonders, girlfriend once wrote me a note about how I "always smell good."
Greenpeople do a range of natural products. Their roll-on works extremely well and is made without pore-clogging Aluminium, Parabens, ethyl alcohol and artificial fragrances.
I tried one of those salt crystals and I thought it was shit! I went straight back to the regular antiperspirants thinking these 'natural' products were worthless but I decided to give them another go and bought a greenpeople product and it worked great!