Those zip stick things you can get at Dollar store work great for hair clogs. They look like a long plastic stic with thorns.
Pour boiling water down the drain. Then add a half cup of baking soda and let it sit for a minute. Pour a cup of vinegar and a cup of hot water down the drain. Cover loosely and let it sit for 10-15 minutes. Pour another pot of boiling water down the drain to flush out the clog.
hometalk has some ideas: