As I wrote in that article for Contagious a while back, I think there is a remix culture emerging, where creativity is collaborative and recombinant. The ultimate expression of this trend so far is the emergence of web mash ups.
By opening up your API, you can allow anyone with an idea to use your technology to build something else - this is a core part of whatever the hell web 2.0 is and it's brilliant: allowing millions of brains to build on your idea makes for cooler and cooler things. Open source and that.
Since I covered it in that article a bunch of new mash-ups have been developed that are worth mentioning, especially Bubblr, which allows you to construct and publish comic strips from Flickr.
Mashupfeed can keep you up to date on the latest mashups.