Using the words TCM in the domain name of the site is definitely a little misleading. Here you will find information from as many styles of acupuncture and oriental medicine that I can find information on. The three main styles that I have categorized are the Chinese style (Traditional Chinese Medicine), Japanese style, and Korean styles (mostly Korean Hand Acupuncture). I will try and supply you with a decent history of each. As always let me know of errors or inconsistensies by emailing me.
Probably the oldest style, with a history of at least 2300 years (good luck finding a real number for that one), TCM has undergone many changes especially in the past century. It's roots lie in the classics of the Huang Di Nei Jing (Yellow Emperor's Internal Classic), the Nan Jing, the Shang Han Lun, and more. The great doctors of acupuncture, through the course of Chinese history, have often varied from great healers to quacks in the minds of the people and government. From China, especially during the 12th and 16th centuries, it spread to the other parts of asia (especially Japan and Korea) and even as far as Europe. At the end of the emperor's reign and the cultural revolution in the middle of the 20th century, much was lost to the Chinese practitioners as they were put second to medicine of the West. In rebuilding their medicine it went through a metamorphosis and began to mingle with herbal medicine and thus became TCM. A TCM style treatment often involves heavy manipulation of the needles and a strong sensations of qi. Also involved may be Tui Na (chinese massage and physical manipultaion), as well as herbal medicine, cupping, gua sha, and other adjunctive techniques.
It is said that the Japanese practice a truer form of medicine than the Chinese since the cultural revolution had little influence on their medicine. Whether it is that differentiation, or simply the uniqueness of their nation, the Japanese style resembles next to nothing of TCM. Many different schools exist, some that even only use moxa to treat. Much of the Japanese styles derive from varying interpretations of the Nan Jing. The Japanese have greatly influenced acupuncture with their technological advances in helping to invent the guide tube, the pump cup (as opposed to fire), and the silicon coated needle. As a general rule Japanese styles are much more subtle than TCM. The needles are inserted shallower and the "De Qi" sensation is not necessarily sought after. In addition, the Japanese seem to place much greater importance to details (i.e., direction of needle, order of insertions, etc.). They also seem to concentrate much more on root treatment than local. Some say that the subtleties extend to outcome and that they are no less pronounced but sometimes slower and less dramatic.
As few teach Korean styles of acupuncture I have little information on them. The little I know comes in the form of Korean Hand Therapy, a recent invention of the twentieth century. Two schools of thought exist here. They regard the hand as a microsystem of the body, much like the ear. The two schools simply differ on the orientation of the body. The first school believes the middle (3rd) finger is the torso and head, with the arms being the 2nd and 4th fingers, and the legs being the 1st and 5th. The second school thought the thumb (1st) the head, the palm the torso, the 2nd and 5th fingers the arms, and the 3rd and 4th the legs. Needling is done on the hand both as local treatment for the ailing part of the body. However, one can also do a full root treatment similar to the Japanese styles all on the hand.