If you fly just pack it well and put it in your checked luggage. I've done it this way many times and never had a single problem. If you drive I wouldn't even worry about it. From US Code Title 27 Sec. 121:
"All fermented, distilled, or other intoxicating liquors or liquids transported into any State or Territory or remaining therein for use, consumption, sale, or storage therein, shall upon arrival in such State or Territory be subject to the operation and effect of the laws of such State or Territory enacted in the exercise of its police powers, to the same extent and in the same manner as though such liquids or liquors had been produced in such State or Territory, and shall not be exempt therefrom by reason of being introduced therein in original packages or otherwise."
The way I read that is that while transporting the homebrew from state to state, as long as you are in compliance with the individual states' homebrew laws then you have nothing to worry about. For most states that means <200 gallons per 2+ adult household or <100 gallons for single adult households and over 21 years of age.
DISCLAIMER: I am not a lawyer so this should not be taken as legal advice.
Reason: Added disclaimer