We used the opportunity of a trip to Seattle to drop by Everett and visit the Boeing factory. It was a blast and worth the three hours. If you have the opportunity, do it. The only one – huge – caveat is that you cannot take with you any electronic equipment. So no photos, but you will have plenty of memories (old school).
The factory floors are ginormous: there were three 747-800 being assembled, six 777 and five 787. From the outside, as well as in the lobby, you can take a picture. I added a few pics from outside the plan and from the expo. Note that the last picture is from another Boeing facility that you may have spotted if you went to the sea-tac airport. Enjoy!