Great post in one of the blogs at boston.com about an commonly-overlooked issue. A parent's ability to help their child with medical issues — like acting as an advocate in the event of an illness — ends when the child turns 18 unless the child has signed a health care proxy and HIPAA-compliant release for medical information. If these documents aren't signed and on file at home, with your kid's doctor and at the student health service, you may not be able to help your child get critical care in the event of a medical emergency.
Similarly, your child needs a durable power of attorney giving you legal authority to access her bank and credit card accounts and to make legal decisions. For example, if your child is seriously injured in an accident, you don't want to have to go to court for a conservatorship just to sue the idiot who ran the ran the red light! The DPOA will allow you to help when help is needed most.