University of Hawaii System
A great start for those just getting into college planning. Run by the College Board, administrators of the SAT.
An application used by over 700 colleges world-wide. Includes a college database, and virtual counseling.
Run by the National Center for Education Statistics, this is an excellent tool to find data on any school you want.
This college search database is especially good at giving you side by side comparisons between schools.
Student reviews sets this college search site apart from the pack.