Mississippi State University Veterans' Certificate 15 sh, online. Can be taken by graduates or undergraduates and either for undergraduate or largely graduate credit. Admission certainly isn't restricted to veterans. SUNY Empire State College Graduate Certificate in Veterans Services 12 sh, online.
Drexel University Online has a graduate minor in services to veterans administered by the Nursing department but potentially available within Drexel's online master's degrees in other fields. "The disciplinary area of the minor may be fully outside the major program or may be related to, but not completely overlapping, the major program."