Is it okay to write a letter to a potential employer after you've sent your resume expressing interest?

A manager in another department at the hospital I work in, asked my old boss (who shares an office with her), if she thought I'd be interested in working for her. My old boss wrote me an email telling me, and I applied for the job. I also heard from another co-worker who works for my potential boss that she said she was definately going to call me. It's been almost a week or so. Should I send a follow up letter or email to the potential boss just reminding her that I'm still interested?

I know the potential boss really well. I just wanted to "remind" her that I'm still interested in the position.

Of course. It will show your interest in the job. In fact, you should call right now and confirm it with the follow up letter.
Peace and blessings!

waiting is tough, but if you call too soon your salary value may depreciate. I'd wait about 3 to 6 weeks and call rather than write. but thats just me.

that is kinda of like a good and bad thing... reason is if you email (or send a letter) they may be like she is really annoying or they may take it as okay thank you for the up date...

It really depends on what you write too... I would keep it general and thank them...

Good luck

I think you should definitely write a letter. Entusiasm is one of the key things that employers look for and writing a letter will show that.