Recently I’ve read some interesting articles about Web APIs and how they open up new business opportunities. The resources below explain this much better than I can, but in summary the web has become more than surfing to pages via browsers. Instead web APIs often cause more traffic to sites than direct page visits.
programmableweb has among other things a directory of web APIs. The growth of web APIs is amazing. As of today they list 5339 APIs.
I like how Sam Ramji describes this new era in this great video:
I started to read two blogs where you can find a lot of more details about this topic. The apigee blog has not only great articles but also several webinars/videos. The other blog is the programmableweb blog.
In order to consume these web APIs in XPages you can use the Social Enabler which comes with the extension library. There is a video showing the social enabler in action.