Just FYI about the Crystal rocks, roll-ons etc. The alum of potassium alum is aluminum sulfate, so...aluminum, albeit in a different form than in commercial antiperspirants.
I've done a little research on them and the companies that make them like to claim that the aluminum molecules are too big to be absorbed by cells or something like that, but I've never been able to find a good explanation for it, especially an explanation that's NOT written by the companies that make them. The best I've found is this: http://www.chemicalforums.com/index....;threadid=3080
Anyway, to me there is no clear answer, so I don't use them. Aluminum and parabens are the two things I think are most important to avoid.
Like a pp mentioned I have had great luck with applying baking soda to my pits AFTER I apply a natural deodorant (I use a makeup brush to dust it on). If I apply baking soda directly to my skin, like if I mix it with coconut oil, I get the dreaded pits of fire. But thankfully not this way. Honestly, I think the natural deodorant is pretty useless on its own, it just acts as a protector on the skin and the baking soda does the actual deodorizing.
The other thing there is sometimes confusion about is the difference between baking soda and baking powder. Baking soda is just sodium bicarbonate and does not contain aluminum. Baking powder contains baking soda and other ingredients. SOME baking powder contains aluminum (interestingly it's usually alum, the same alum in the crystal deodorants! But sodium alum rather than potassium alum). So it's a good idea when buying baking powder to make sure it says "aluminum free". I think the aluminum free ones contain cream of tartar instead of the alum.
Okay, I'll get off my geek soapbox now.