Here's one for LazyWeb: the marriage of WatchThisPage and RSS ifier. Call it SyndicateThis!
WatchThisPage was the name of a service that let you know by Email when webpages were changed. Watchit.US seems to be a successor.
RSSifier is a voidstar utility allows bloggers whose blog software does not have automatic syndication to syndicate their blogs. But the blogger has to modify his/her template.
So, combine a "diff" utility service a syndication service. If there's a page I want to track (without cluttering my email inbox), I use a form to as SyndicateThis! to keep tabs on it. SyndicateThis! returns a URL for an RSS feed that generates an item each time the watched page changes. The item shows the nature of the change.
(Or maybe this exists already?)