The Chances Of Finding A Shiny:

What makes a shiny a shiny is its stats that it was born with - these are called the IVs, i think (stands for individual values)
let me explain.
if you just keep catching pokemon of the same level and species, you will notice that their stats vary. the greatest amount a stat can vary from one pokemon to the other is 15. say i have found a secret location that only has one species of pokemon in it, and they are all at level 100. and say the lowest speed stat i ever saw on the this pokemon is 30. that means that it has zer0 Individual Values. and the highest one i ever saw - and will ever see - was 45. that pokemon has IVs of 15. get it?

now, shinies must have these IVs to be shiny:
attack: 2, 3, 6, 7, 10, 11, 14 or 15 so there is a 1/2 chance of the wild pokemon getting this right
def: 10 - 1/15 chance of getting this right
spec. att: 10 - 1/15 chance of getting this right
spec. def: 10 - 1/15 chance of getting this right
speed: 10 - 1/15 chance of getting this right
hit points: do not play a part in getting shinies

so lets multiply them to get our answer:
1/2 times 1/15 times 1/15 times 1/15 times 1/15 =
2,531 out of every 10,000,000 pokemon rounds off to one in every 3,951 pokemon. And these odds are independant, which means that even if you have seen 3,951 non-shiny pokemon, you still have a 1/3,951 chance of finding one

IVs also determine what hidden power you get, and shinies get either:
-hidden power grass, 50 base damage
-hidden power dragon, 50 base damage
-hidden power grass, 70 base damage!
-hidden power dragon, 70 base damage!

but its too hard to explain how IVs (sometimes called DVs) infleunce hidden power, so heres a link to a site which CAN explain that! http://dynamic3.gamespy.com/~psypoke/gsc/dvguide.php

Note: in Ruby/sapphire, there is a different system of IVs. they vary from one to thirty-one, and make it EXTREMELY difficult to get a shiny or a pokemon with the right hidden power.

Anyways, i just got a shiny onix! (it was such a shock when i heard that twinkling sound at the start of the battle):):)and in crystal, i have a shiny crobat!:):):)
just post some of the shinies you found here!