This is just a small sample of the Internet sites with oral histories, diaries, memoirs, journals, letters, etc. from veterans of World War II. There are many local projects throughout the United States. If you're looking for stories about veterans from a particular geographic location, look at the local museums, archives, libraries, etc. There are also veterans' groups for some of the divisions, ships, camps, etc. and some of those provide oral histories on their website.
This box includes links to resources about World War II from all over the world.