The NARA has a Archival database called WW II Electronic Army Serial Number Merged File 1938-1946. There are Two parts. One is Enlistment Card Records and the other is Enlisted Reserve Corps Statisical Card Records. It has over 9 Million Names of Enlistes. With the the Enlistes name are some basic info about the person. This might help someone who just start to do research.
Also at the NARA is a WWII Prisoner of War File ca.1942-ca 1947.