http://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/yellowstone_page.html
http://www.mines.utah.edu/~rbsmith/RESEARCH/YellowstoneHotspot.html
http://www.seis.utah.edu/yvo/index.shtml
http://volcanoes.usgs.gov/yvo/
http://www.solcomhouse.com/yellowstone.htm
http://volcano.und.nodak.edu/vw.html
Enjoy!