Most PhD in the US are funded, but are not really advertised. The best thing to do is to find the uni you are most interested in applying to and a supervisor in your area of interest, (may also have pages on how to apply on the web), and contact him or her for information, problem is that there you have to pay for applications which can be pricey. its also likely to be 5yrs PhD as involves lab rotation and a masters, I think before hand.