Below are the individual forces and a little bit about what they offer. Much of this is taken from www.military.com - Another good website if you would like to get more information.

US Air Force

The Air Force defends the United States through control and exploitation of the air and space. The men and women of the Air Force fly, maintain and support the world's most technically-advanced aerospace vehicles, including long-range bombers, supersonic fighters, Airborne Warning and Control System (AWACS) aircraft and many others. The Air Force operates satellites, missiles and America's early warning systems.

The Air Force is made up of nearly 385,000 men and womendisciplined, dedicated and professionally trained officers and airmenfrom all walks of life. Air Force people multimillion-dollar aircraft, launch satellites, gather sensitive intelligence data, manage maintenance and other logistical support, or do one of many tasks vital to the Air Force mission. The Air Force currently commissions about 5,000 male and female officers each year to fill openings in a wide variety of challenging careers.

US Army

The U.S. Army offers many jobs ranging from general administration to the operation and maintenance of the Army's many high-tech weapons, vehicles, aircraft and electronic systems.
As a team, soldiers protect the security of the United States and its national interests.

The Army stands constantly ready to defend our national interests and our allies through land-based operations anywhere in the world.

The Army needs approximately 80,000 to 90,000 new enlistees each year. Those who enlist into the Army find hundreds of challenging careers offering a lifetime of security and excitement.

US Coast Guard

The U.S. Coast Guard ensures maritime safety, saving lives and property in and around American waters.
The Coast Guard also enforces customs and fishing laws, protects marine wildlife, fights pollution on our lakes and along the coastline, and conducts the International Ice Patrol.

It also monitors traffic in major harbors, keeps shipping lanes open on ice-bound lakes and maintains lighthouses and navigation aides.

The Coast Guard is a part of the U.S. Department of Transportation. In time of war it may be placed under the command of the Navy Department. A vital part of the Armed Services, the Coast Guard has participated in every major American military campaign. The Coast Guard is the smallest of the armed services. Currently there are 5,864 commissioned officers, 1,520 warrant officers, and 29,839 enlisted members. Coast Guard officers perform in many different occupations to support the mission of the Coast Guard. Each year, the Coast Guard has openings for about 300 new officers in a wide range of challenging careers.

US Marine Corps

The Marine Corps is one of the most elite fighting forces in the world. The Marines are a part of the Department of the Navy and operate in close cooperation with U.S. naval forces at sea. Marines serve on U.S. Navy ships, protect naval bases, guard U.S. embassies and provide an ever-ready quick strike force to protect U.S. interests anywhere in the world.

To perform the many duties of the Marine Corps, approximately 174,000 officers and enlisted Marines fly planes and helicopters; operate radar equipment; drive armored vehicles; gather intelligence; survey and map territory; maintain and repair radios, computers, jeeps, trucks, tanks, and aircraft; and perform hundreds of other challenging jobs. Each year, the Marine Corps recruits approximately 41,000 enlisted men and women to fill openings in its numerous career fields.

Marine Corps training programs offer practical, challenging and progressive skill development. The Marine Corps stresses professional education for all ranks and emphasizes the development of mental strength as well as traditional physical prowess. In this way, the Marine Corps provides the nation with a modern, well-armed force that is both "tough" and "smart."

US Navy

The Navy defends the right of our country and its allies to travel and trade freely on the world's oceans and helps protect our country during times of international conflict. Navy sea and air power make it possible for our country to use the oceans as our national interests require.

The Navy is a large and diverse organization. It is made up of about 400,000 officers and enlisted people. Navy people operate and repair more than 340 ships and over 4,000 aircraft; they serve in diverse fields like communications specialists, dental hygienists, computer programmers, ship electricians, and work in many other exciting careers.
Navy people serve on ships, on submarines, in aviation positions on land and sea, and at shore bases around the world.

The Navy recruits about 60,000 officers and enlisted people each year to fill openings in Navy career fields.

Conclusion:

Each force has their own individual advantages. Whichever career or career field you choose, the military can help you get there.