Chemistry
IMF Bridge
1.1 Patterns in Matter
Setting the Table
Periodic Table Resources
There is another...
Building Atoms
Patterns of the P-Table
Lots of interactivity and information. If you want to explore different units (mmol, stp, MPa, and many more) this is the site for you.
PeriodicTable.com - A collection of searchable elements with TONS of info about each element.
Just as it sounds, this is a site with videos about each of the different elements and much more.
With this site you can select a variety of properties and see their relationships.
LOTS of ads.
First Ionization Energy of the elements.