Paul Tibbets B-29 - Enola Gay online tour here. It takes a bit of time to load:
http://www.davidpalermo.com/data/slideshow/4/index.html
It may be your last chance to get inside.
Here's several more virtual cockpit tours. Give it time to load. Some of the cockpits are ol'school and there
are modern ones on this site too.
http://blog.360cities.net/airplane-cockpits/