To (Supervisor's name)
From: (Your name)
This will confirm my resignation as (your title) at (company name). I have accepted a position as (your new title) at a growing (type of company, not company name) company in (state). I am looking forward to my new position and the challenges that await me. My decision, although a hard one, is firm.
My last day of work will be (date), which should allow me plenty of time to finish ongoing projects and to turn over my position to my replacement. Please feel free to contact me at any time should you have any questions regarding my past work. I hope that the transition will go smoothly for everyone.
My experiences at (company name) have been very rewarding. I appreciate having had the opportunity to work for such a fine company. I wish you and the organization continued success.
Supervisor's name & title
Dear (Supervisor's name),
This is to inform you that I have been presented with an opportunity that will enable me to work in the area of my stated preference, (indicate discipline such as sales/engineering/etc.). Therefore I am tendering my resignation with (company name) and wish to advise you that (date) will be my last day of employment.
I would like to thank you for the experience of having worked for (company name), a truly outstanding organization.