The only surefire way to reset the clock on a VWP stay is to leave the US and travel to a country outside North America and the Caribbean. The only way to do this without crossing any oceans is to go south of Mexico - all countries in Central and South America, from Guatemala on down, are not listed on the CBP website as countries which do not reset the clock on a VWP entry.

http://www.cbp.gov/xp/cgov/travel/id...re/vwp/vwp.xml

I would suggest a long weekend in Costa Rica or something along those lines.