I’ll second the post that said “The CTCL schools,” though there are plenty of schools that could easily be included in the CTCL book but are not, places like Luther (IA), Lake Forest (IL), Lewis & Clark (OR), Coe College (IA), Muhlenberg (PA), William and Hobart Smith (NY), Washington C. (MD), and so on. Then there are the much more regional LACs that have solid reputations: Albion (MI), Augustana U. (SD), Augustana C. (IL), Lycoming (PA), Illinois Wesleyan (IL), Nebraska Wesleyan (NE).
Truth is, there are too many hidden gems to list, and the list will always be highly subjective. Remember, too, that even the most elite of LACs are virtually unknown to most people. If you wish to humble-brag that you attend (or your child attends) Oberlin, most people’s response will be, “What is Oberlin?” Thus, all LACs are in a way “hidden,” though the gem-like ones will be those that offer top-notch educations but are A) 10-15K cheaper than “elite” LACs in the NE, and, B) are not as cutthroat to get into.
If I were to include public universities, I would list Ohio U, which some people confuse with Ohio State. Ohio U is the state’s oldest school, is more than half the size of Ohio State, has one of the most gorgeous campuses you will see, and absolutely competes with Ohio State for the state’s top students (a majority might end up at Ohio State, but some simply prefer Ohio U for the reasons I listed above). I would also give a shout-out to public LACs: SUNY Geneseo, UNC-Asheville, St. Mary’s of Maryland, U. of MN-Morris, the New College of FL, and Truman State (MO).