RocketBar – A jQuery And CSS3 Persistent Navigation Menu
The way it works is that when a user lands on your page they get to see the default navigation as usual. If they decide to start scrolling however, the top navigation detaches itself from the page and follows you as you scroll down. If you decide to go back to the top of the page (for whatever reason) the navigation goes back to the way it appeared before. This technique isn’t just limited to showing you the default menu in a way that detaches itself from the page, but the code could very easily be modified to show a completely different menu for those that scroll down