codepope pointed
the TFL Journey Planner out, but I thought it was such a good example of a web application I had to share it all over again. Enter where you are, and where you want to go and it'll give you an integrated journey plan for bus, train, tube, and even boat - as well as walking.
Excellent work, and a really useful resource that goes straight onto my bookmark list...
But it's not enough. Personally I think, what it needs is a RESTful interface, or a SOAP/WSDL interface. I don't care which, I just want to build this into existing web sites all over London... But there isn't one. Just a web page.
So, six out of ten for effort. two out of ten for execution.
Think that little bit further guys. Take a look at the Amazon API and try again.