Like Binu said, there is no standard format for resignation. Resignation is a personal decision of an employee and how he gives expression to this decision is again, his personal choice..of words and expression.
I can asure you that framing a resignation letter is a matter of skill. In my long work experience, I have helped several people to draft their letters of resignation.
A wrongly worded resignation letter can easily lead to sure disaster.
Cheers!!!
Vasant Nair
Director
Karma-HR