1. GI Bill Programs such as the Montgomery GI Bill and Post 9/11 GI Bill (with the latter seeming to be the standard now, e.g., I used Post 9/11), Tuition Assistance, Tuition Assistance Top Up Programs (if the cost of course exceeds the amount covered by federal TA), Enlisted College Loan Repayment Programs. Note: Post 9/11 used to have a time cap but with the Forever GI Bill Harry W. Colmery Veterans Education Assistance  Act has expanded a lot of opportunities for the 9/11 GI Bill. Note: Always consult the VA.
2. The VA’s Survivors’ and Dependents’ Educational Assistance Program
3. Federal US Service Academies (West Point, Air Force Academy, Naval Academy, and, yes the Coast Guard and Merchant Marines, etc.); Senior Military College such as The Citadel and Military Junior Colleges such as New Mexico Military Institute (which can provide a pipeline into a Senior Service Academy but they also offer ECP or Early Commissioning Program which is more catered to the Army and allows cadets to commission in two-years as opposed to four-years in the Army Reserve or National Guard),
4. ROTC in general
5. Some States offer Running Start-type programs permitting high school students to attend local community colleges while in high school and obtain an Associates Degree. So imagine being 18 with an Associates Degree for example from Tacoma Community College, then going to a 4 year school, only needing 2 years (or taking your time), doing ROTC such as Pacific Lutheran University or going to a Military Junior College and then getting commissioned as a 2nd LT in the Army Reserve and National Guard, potentially serving at Camp Murray in Tacoma, and then using the TA from that to attend graduate school, let’s way UW-Seattle or Tacoma. Basically, in this list, you can see how you can potentially mix strategies for affordable education. 
6. Some states offer Hope Scholarships such as Georgia which is funded by the lottery and pays for in-state public college tuition, but states how they administer these programs vary, e.g., some pay all, others might only give grants.
7. Segal Education Awards through programs such as the Peace Corps, AmeriCorps, and I want to also include Teach USA. Also, many colleges are Matching Institutions. If I remember right, it is taxable however. 
8. Trade Union scholarships such as the American Postal Worker Union (https://www.apwu.org/scholarship-programs), Communication Workers of America (https://cwa-union.org/pages/beirne), Union Plus (https://www.unionplus.org/benefits/education/union-plus-scholarships), United Auto Workers (https://uaw.org/apply-now-union-plus-scholarship-program/). AFL-CIO branches through States,(https://www.massaflcio.org/scholarships), etc. International Brotherhood of Electrical Workers (http://www.ibew.org/FoundersScholarship).
9. Corporate Scholarships and Corporate/Employer-based Tuition Reimbursement Programs
10. Private scholarships such as organizations such as 4-H, Kiwanis (Key Club), etc.
11. Certain states such as Washington State offer Head Start Programs giving high school students the ability to graduate with an Associates before high graduation.
12. 529 Savings Plans (Note: I am not a financial consultant. Always seek professional advice) which is sort of like an “educational mutual fund and savings account”.
13. Pell Grants

Some Links:

https://www.benefits.va.gov/GIBILL/comparison_chart.asp