Check out deviantArt's infinite scroll implementation. If you go to their home page, and scroll to the bottom, there's a big green "Show More" button. No infinite scrolling happens until you explicitly want it to and you are able to get to the stuff in the footer. Once you start scrolling, it's very fast and there's not much of a delay as it loads more things. It also updates the URL as you scroll so when you click on something and hit the back button you are where you left off. It's quite slick.