Common chemical names are easy to find on the internet, if they exist. Just copy and paste the formula into a google search and you'll get a bluzillion hits. If you want to know common names in order to discuss chemistry you're better off using the chemical industry name for the compounds.
The IUPAC, International Union of Pure and Applied Chemistry, convention for naming inorganic compounds is simply to use the elemental name and number of atoms in the compound starting from left to right. If there are common molecular compounds within the compound, such as Bicarbonate, Phosphate, or Sulfate, those are used.
http://www.iupac.org/dhtml_home.html
KH2PO4 would be Potassium Dihydrogen Phosphate, not Potassium Dihydrogen Phosphorous Tetraoxygen.
In common use terms if there are multiples of the same element attached to one other molecule the multiple is dropped.
K2SO4 would be Dipotassium Sulfate according to the IUPAC nomenclature conventions, but Potassium Sulfate is what it is commonly called.
If you want to get into organic molecules you're on your own.

Those are a bear to name and are why you see such huge names for things in your shampoo.
Interesting site I found when looking up KNO3-
http://www.vro.be/research/propellan...gar_page6.html
I hope this has helped some,
Phil