I have always found drain cleaners to be scary and toxic - I hate to have them around the house with the kids.  So when I happened across this natural drain cleaner recipe, I was thrilled.  This is one of many recipes out there - but the basics are just baking soda and vinegar - something everyone tends to already have around the house.  Note: this will not work on really horrible clogs, but it is a great tool for "regular maintenance" of your drains.  And the chemical reaction is fun too (and safe).

Drain Cleaner
1/2 cup baking soda
1/2 cup white vinegar
Boiling water

Pour baking soda down the drain. Add white vinegar and cover the drain, if possible. Let set for 5 minutes. Then pour a kettle of boiling water down the drain. (The vinegar and baking soda break down fatty acids into soap and glycerine, allowing the clog to wash down the drain.) Do not use this method if you have used a commercial drain opener and it may still be present in the drain.