My drain in the bath room was running slow the other day and I remembered a non-chemical way to hopefully get it flowing again. It is baking soda and vinegar. You dump about a 1/4 cup of baking soda in the drain and pour the vinegar over it. Its just like making a volcano, it fizzes for a while. I let mine set until next time I had to use my sink and now it works perfectly without any scary drain uncloggers.
Using something that well I can eat to unclog my drain is pretty cool. I am not sure how it would work on a completely clogged drain but a slow one, it works really well. It is also recommend you do it regularly just for maintenance of the drain. It makes everything smell nice too.