I don't necessarily endorse any purchases through this site but I thought it was interesting to see what it had to offer (even though this information is probably all publicly available anyway).  FBI files on figures such as[url url=http://=http://www.paperlessarchives.com/guevara_.html]Che Guevara[/url] and Al Capone; UFO files; audio recordings of interviews with former slaves; OSS files on Hitler, and much more.  I suppose if I were researching a particular topic some of this information would particularly come in handy.