Biotin
I take 5000mcg 1 time per day. Not sure if it's helping or not because I'm still losing hair, but to tell you the truth, I figured I wouldn't be able to completely stop it from happening. It's not horrible, but definitely noticeable when I'm decorating my shower wall. I also use Nioxin, but dang, that stuff is expensive. It'll grow back, so I'm good with how it's going so far.
I buy my Biotin at Walmart. (Spring Valley brand, Super Potency Biotin 5000 mcg capsules) I take one a day. I've been taking it for about a month and I just noticed that my hair loss seems to slowing down this week. Either its the Biotin, a fluke, or natures way of saying, "OK you've suffered enough."