I use Desert Essence's "Dry By Nature"...my dh prefers Alba's "Active Enzyme" line. You can buy them at Whole Foods, Sprouts, or any other "health food" store. Here's a link:
http://www.evitamins.com/product.asp?pid=4408
The important thing to remember about these products is that they work best OVER TIME. Desert Essence actually uses herbs that inhibit the sweat glands under your arms naturally. Now...if I am doing yard work in the summer...I'm still going to sweat!! However, if I am just doing daily activities, I rarely sweat under my arms any more. Also, there are natural ingredients that inhibit bacterial growth (which causes the famous "smell") in this deodorant. So, even when I do sweat...there is rarely an odor.
I was very surprised to find a product that worked as well for me as a "regular" anti-perspirant. I think I used to sweat so much under my arms because my body was trying to "flush out" the aluminum and toxins present in the anti-perspirant. I never thought THEY could actually be causing me to sweat!!!