James Padolsey's jQuery scrollstop plugin that fires an event when scrolling stops for minimum amount of time.
Originally code copied from http://james.padolsey.com/javascript/special-scroll-events-for-jquery/
jQuery.event.handle.apply is not available in jQuery 1.7+ so I replaced it with a call to jQuery.event.simulate seems to work for me in conjunction with tuupola's lazyload.