Ullmann's Encyclopedia of industrial Chemistry - 7th. ed - 2006 - short and concise overview of existing knowledge about compounds, processes a.o.
Ptable - excellent presentation of all the basic properties of the elemsnt
FACULTY OF CHEMICAL TECHNOLOGY IN SPLIT - PERIODIC TABLE OF THE ELEMENTS - contains also comprehensive tables of redox-potentials, isotopes, energy of ionisation a.o.
EnvironmentalChemistry.com - contains information about environmental chemistry of the elements
Periodic Puzzle - with coloring control to shade the table according to the values of the physical or chemical properties of the elements
YouTube-videos (University of Nottingham)