Chemicool
http://www.chemicool.com/
It's Elemental: Periodic Table of Elements
http://education.jlab.org/itselemental/
Periodic Table of Elements LANL
http://periodic.lanl.gov/index.shtml
Periodic Table of Elements by WebElements
http://www.webelements.com/
Periodic Table of Elements | Minerals Education Coalition
http://www.mineralseducationcoalition.org/periodic-table-elements
ChemicalElements.com
http://www.chemicalelements.com/
Dynamic Periodic Table