To add to what’s already listed…
USAF Special Operations - Aireal insertion of other services’ special forces, operation of AC-130 gunships and other specialized aircraft for psychological operations, communications, and other missions. Also combat search and rescue. Air Force Pararescue Jumpers (PJ’s) are part of Special Operations Command.
Navy Underwater Demolitions Teams (UDT’s) - AFAIK these teams are still a separate entity from the SEALS.
Marine Expeditionary Units (Special Operations Capable) - technically not special forces, but they are trained and capable of assisting with special missions.
Marine Force Recon - USMC special forces, for lack of a more detailed description.
The Green Berets are more properly known as US Army Special Forces and they do a hell of a lot more than “train insurgents in foreign countries”. Special Forces take on covert missions with minimal support often behind enemy lines. Every special forces trooper is fluent in at least one language in addition to English, and most of them have some kind of medical training. They also find themselves conducting humanitarian missions quite a bit as well. A lot of schools and clinics in the so-called “Third World” were built by our Special Forces troops. They also train indiginous military forces - not “insurgents” most of the time - which are allied with the United States. There is not organization within the US Army known as “The Green Berets” - that is an unofficial nickname which refers only to their headgear.
Wes, I would suggest going to http://www.soc.mil/ (Army Special Operations Command), http://www.sealchallenge.navy.mil/ (Navy SEALS), www.usmc.mil (cound’t find anything more specific on the Marines…so sue me…) and http://www.afsoc.af.mil/ (Air Force Special Operations Command) and poking around a bit to find out more about the various special forces units. Your suppositions, while somewhat accurate, are waaaaaay simplified and a little off-base.