Flickr without the Flash
Neil also touches on the fascinating cultural issues brought up by userscripts:
Lately I’ve been considering Lickr as an experiment in web politics. Exactly how far can the users go in controlling a website? Right now I’m at the point where I can stop thinking about just duplicating Flickr; I can think about adding features.
Adding Persistent Searches to Gmail has already demonstrated new features enabled by userscripts, and that’s evidently just the tip of the iceburg. Plans are underway to provide greasemonkey with its own persistence mechanism. Once that happens, the sky’s the limit.