The blog Metal Floss recently ran an article (http://mentalfloss.com/article/20848/6-tuition-free-colleges) documenting 6 tuition free colleges in the US:
1) COLLEGE OF THE OZARKS (Point Lookout, Missouri)
2) DEEP SPRINGS COLLEGE (Inyo-White Mountains)
3) BEREA COLLEGE (Kentucky)
4) OLIN COLLEGE OF ENGINEERING (Needham, Massachusetts)
5) CURTIS INSTITUTE OF MUSIC (Philadelphia)
6) ALICE LLOYD COLLEGE (Pippa Passes, Kentucky)
How it's funded: oftentimes an endowment covers the cost, working for the school seems common, the school accept very small numbers of students, and there seems to be a clear public interest/giving back focus to these schools.