In addition to the Trask article Lew links to, I'd like to suggest these resources:
And see the really cool Independent Institute archive on Pearl Harbor here. Look especially at some of Stinnett's articles. See also the debate between Stinnett and Stephen Budiansky, author of Battle of Wits: The Complete Story of Codebreaking in World War II — the link to this last one is broken in the archive.
And here's an article I wrote three years ago about why I thought no one really cared about this stuff.