Keep your foot in the door of an old job by offering contract services with this partial resignation letter.
November 17, 2014
Dear Mr./Ms. Bossname,
This letter is to inform you that I must tender my resignation, effective (date).
It has been a great pleasure to work with you and be a part of (company)'s growth. I wish you all nothing but success in future endeavors.
I would be open to consulting with the firm in the future, and have set my hourly consultant fee at $150. Please don't hesitate to call or email if you require my services.