I was just monkeying around with Yahoo's new SearchMonkey Developer Tool and it seems to be the closest thing to helping users build a "blog-wiki-mashup-with-video-share" application so far. It also has the simplest interface I have seen to create data services and publish them for broad (or narrow) consumption. They even give you the PHP code if you want to run the service on a non-Yahoo site.
There are two main audiences for the SearchMonkey Guide:
SearchMonkey developers are front end engineers who build presentation applications, small PHP applications that enhance search results. Most presentation applications are fairly simple and do not necessarily require deep working knowledge of PHP.
SearchMonkey site owners are site owners who are responsible for delivering data about their site's pages for SearchMonkey developers to build upon.
Site owners are responsible for data, while developers are responsible for presentation. Smaller projects might assign the developer and site owner roles to the same person, but larger projects tend to have more specialized roles.
This functionality will likely be glossed over by Yahoo's ongoing shareholder ordeal, but the innovation here proves that Yahoo has a lot more going on than we generally give them credit for. They also did a really nice job of documenting everything--which is a general engineering nightmare.