The folks at Humanized had a nice idea that seems a perfect use of AJAX. They proposed that a user interface could get rid of the page chunking links you see at the bottom of search results lists and instead, dynamically add more entries to the bottom of the page as the window is scrolled. To prove the concept, they've implemented this idea in a news feed aggregator. They call this automatic expansion of the list of entries "Humanized History".
Scrolling in GoogleReader is essentially the same. There are two panels, one on the left to scroll the entries titles and one on the right for viewing the individual entry selected on the right. Humanized Reader does it all in a more typical blog-format, with a simple reverse chron list. Google Reader is more like a conventional application UI, but has the same page-less model.
The concept is very powerful. Using technology appropriately, let the interface get out of the way when possible so that people get right to using the content. Humanized does this with a design that is simpler and more elegant than the Google Reader. They say the point is to let you spend more time reading and less time thinking about navigation. Put another way, they say, "Don't force the user to ask for more content: just give it to them." Sounds like something Steve Krug would agree with. I like it.