All branches of the military except the Coast Guard have a Reserve Officers Training Corps that provide college scholarships in exchange for spending time in the service after graduation. The length of the commitment varies depending on the service and the military job you sign up for. A basic Army commitment, for example, is eight years of service --- but only four of those years are served on active duty. The remaining four are served in the "Individual Ready Reserve." Air Force pilots have a 10-year commitment. Check the websites for each branch of the ROTC for specifics.
The most direct and obvious benefit of joining the ROTC is that you get money to go to school. Two-, three- and four-year scholarships are available that pay full tuition and provide an allowance for books and fees. You may also receive a monthly living allowance of a few hundred dollars a month.
Going through ROTC gives you a leg up when you do enter the service --- you begin your career as an officer, which means more money and better living conditions than if you first serve as an enlisted person and go to school after you get out.
ROTC provides leadership training and experience that you're unlikely to get in other college courses. You will also have physical experiences --- parachuting is one possibility, a day on a rifle range is another --- that other students won't.
The demands of Iraq and Afghanistan have forced many service members to spend time in places and jobs that are far from what they thought they signed up for. Explosives experts from the Air Force have been called on to defuse roadside bombs in Iraq and Afghanistan. Sailors have provided security for convoys traveling on dangerous roads in Iraq. Members of the Army reserves and National Guard have been called to active duty and spent long deployments in combat zones.
You can lower your odds of going to a combat --- taking an administrative job in the Air Force or Navy, for example --- but if you are needed, you are expected to go. That is the price of accepting a military scholarship.
If you are ordered to a combat zone and you refuse to go, you can be court-martialed, which can lead to a dishonorable discharge and jail time.
In 2006, Army 1st Lt. Ehren Watada refused to go to Iraq with his unit because, he said, he had come to believe it was an illegal war. When he did not report to deploy with his unit, he was charged under the Uniform Code of Military Justice --- the set of laws that govern military life --- with one count of missing movement, two counts of contempt toward officials and three counts of conduct unbecoming an officer. He was facing a dishonorable discharge, forfeiture of pay and seven years in prison. In the end no decision was reached as Watada's court-martial ended in a mistrial.