Have you heard of mashups? If you haven't, you will. The term originated with musical examples (like the Grey Album), but now the term is being applied to technological examples, like this cool little calendar widget from 30 Boxes:
This shows a) my blog posts, b) my flickr shots, and c) Drop Trio's show calendar all in one single live calendar (you can scroll forward and back, too).
This kind of cool stuff is possible because of an age-old programming concept that's only now coming into its adolescence: the separation of content and presentation. Keep your data logically separated from how that data looks or where it goes, and you've got all kinds of magic powers. Programmers have been talking about it for the longest time, but only now, I think, is it starting to sink in to our shared consciousness.
By the way, there were a couple others mentioned by TechCrunch today, including a Google Maps one that looks pretty cool.