this is not a difficult task. make it short and sweet.
dear manager, i am resigning my position as staff nurse effective three weeks from today (put the actual calendar date there). you can also add:my reason for resigning is that i have found employment elsewhere. thank you for the opportunity to work at this facility.
thank you, grinnurse
the most important thing about this letter is (1) the date at the top of the letter, and (2) the date of resignation you put in the body of the letter. call personnel and ask them how many days notice they require. some places will want you to put a reason for terminating, but it is not required. the letter is merely a document that memorializes your last day of employment, nothing more. personnel needs to know it. unless you trash the place or the people you work with in the letter it is merely going to get placed in your personnel file and probably never looked at again. everything else is just extraneous, so feel free to express nice things you might want to say, but it is not necessary. if you want someone to listen to your concerns about patient safety issues or lack of supplies, the appropriate way is to ask for an exit interview. at the exit interview, let it rip! if you want to express warm feelies for your manager do it privately in her office or write a separate letter to the don singing her praises. the accolades or criticisms people put into these resignation letters are usually ignored and only end up serving the emotional need of the writer of the letter. anyway, the less you say, the less you have to make appologies or explanations for later. make sure you keep a copy for yourself, just in case. over the years i also started keeping track, in my address book, of the address and phone number of the hospital along with my actual dates of employment, hourly salary, and my supervisor's name as these are things that are commonly asked on employment applications and 7 years from now you won't remember all that stuff.
good luck in your new job!