Technically, I believe it is illegal to transport alchol across state lines (Does anyone know if I am correct here?)
However, if you just have a bottle for personal use no one ever seems to say anything. I would pack it in my carryon. If it is not still sealed, they may make you take a drink from it to prove it is safe so either carry a new bottle or be prepared!
I did sit next to two people on a plane recently who had their own vodka. They had tranferred it into a water bottle.