on your tour screen, create proper thumbnails of the screenshots, don't make the browser download the huge files and scale them itself. it's painfully slow and the scaled versions aren't readable.
Some quick things that would help:
* use :cache => true for both your CSS and JS files, this helps more than you'd guess
* make sure passenger is serving your static content without hitting the rails stack. I don't know much about passenger, but you should check on this.
* as 'there' said, use properly resized thumbnails.
Thanks for the tips on Passenger. I'll take a look at it...
Your comments are much appreciated.