From the NLI site...
Currently 55 conferences are members of the National Letter of Intent program and more than 500 institutions participate. All NCAA Division I institutions, with the exception of those in the Ivy League, which does not award athletic scholarships, the Service Academies and some schools in the Patriot League, are members of the program. Additionally, all fully active Division II institutions are members. No Division III institutions, NAIA programs, preparatory schools, junior colleges or community colleges are members of the National Letter of Intent program. All members of the NLI program are required to offer athletics scholarships. For a list of member institutions, please see the searchable list of
Member Schools.