Science project - Oxidation states

Hi Geeks,
I have been trying to make a science project for my school science exhibition. As, I love Chemistry, i have decided to make a Science project named 'Oxidation State'.

In this project I have to describe oxidation state, its uses, its importance in chemistry and finally some experiments to prove the fact :
"Different elements at different oxidation state can have different properties"

I have collected few compounds of elements at different OS, and they are:
= CuSO4 (Cu at +2 OS)
= CuI (Cu at +1 OS)
= MnO2 (Mn at +4 OS)
= KMnO4 (Mn at +7 OS)
= I2 (I at 0 OS)
= K2S2O5 (S at +4 OS)
= ZnCl2 (Zn at +2 OS)
Sorry, that much only

If you can, please give suggestions about :
>Importance and significance of OS
>Uses and problem regarding elements in their different OS.
(Like this fantastic use: Importance of oxdiation state in blood)
>any more compounds as example
>experiments to distinguish their OS