You've seen it before - you scroll to the bottom of a page and the page loads more content without you clicking on anything. Neat.
I can't think of a better use for this than 'latest activity' feeds - and the clever chaps at 37signals have incorporated 'infinite scrolling' into the Highrise activity feed.
So simple, but will no doubt save thousands of people thousands of mouse clicks.
Highrise: Small Business CRM