How a Mass Spectrometer Works
How a Mass Spectrometer works (video)
YouTube animation of Rutherford's experiment using alpha particles(Helium nuclei decay products from a radium source) and very thin gold foil (about 100-200 atoms thick). Rutherford's Gold Foil Experiment
Table of the Isotopes
Los Alamos Interactive Periodic Table
Here are some other resources that you can't find on the internet: School Library Local Public Library