1 cup baking soda (first)
1 cup white vinegar (second)
allow to foam for 5 minutes
1 gallon boiling water
I have to admit I was skeptical, but it definitely helped the clogged drain we had in our master bathroom. But I think we waited to long to try something to really see the benefits. Had we done this right when we noticed that the sink wasn't draining quickly, I think we would have been much better off than what we actually did, which was wait until the water completely stopped moving.
It was not pretty. So not pretty, I avoided all pictures. You wouldn't have liked them, trust me. But we did learn a valuable lesson about responding early. A lesson that came in very handy with our water heater. I'll tell you more about that later.