The most reliable place online that I have found is www.petersons.com.  It was recommended to me by my college.  Also, if you have a particular college in mind, check with that college--they usually have scholarships specific to their own institution.  If she has a particular major in mind, go to the major website for the proposed college, sometimes they have other scholarships that are not listed with the main college because they are department specific.  Don't forget to look on the Department of Education website for federal aid, and your state's education website for state-specific aid (i.e. lottery money, etc.).  Check with the employers of immediate family members--larger companies/firms often offer scholarships.  The chamber of commerce may have information about local clubs/associations that you can contact.  Watch the business news section of the local paper--when organizations give scholarships, they often are written up for them.  Don't buy books, they are usually at the local library and DO NOT pay an online service to locate scholarships for you unless you truly do not have time to do the above because everything they do can be done by following my suggestions.  Finally, contact the guidance counselor at the high school.  If your daughter is planning to go locally, they often have a wealth of information and/or contacts.

Wendi