Add multiple user accounts at one time

I am looking for a method or tool/program to add multiple users at the same time, as opposed to creating accounts individually. I have not looked into this in the past, but I now have 2 different people that have asked me this question in the last 24 hours. Any help would be greatly appreciated. I am needing to have an answer by 8 am central time Monday morning. (Nothing like a deadline that blows the weekend for you.)