US News & World Report issues an annual graduate school rankings. I know they rank nurse midwifery, nurse anesthesia, and a few NP/CNS specialties. I believe the most recent one came out around August. You may still be able to find it in the stores or your local library should have it. It's also available on their website, but you have to pay to get the details. Also, they do not update all their rankings every year. I believe their most current nursing rankings are as of 2003.