I hope my comment above wasn't too sharp! But I do think finding inspiration is a good idea.
Also, I should add that my Google Reader subscriptions have become a great inspiration to me. When I find sites like the ones above, I subscribe. Here's another really cool site I have come across focused on hacking the Kinect (the name says it all) - http://kinecthacks.net/
Another source of inspiration I have found is locating data sources and creating mash-ups. E.g. http://mashupaustralia.org/data-sources/
It always helps to have some sort of data to work with. I like to think of it as the fuel of an application, where the coding is the engine (maybe that was a bit wishy-washy for stack-overflow, but you know it's true). Your data source could be from a pre-compiled database (like the one above) or it could be collected from somewhere else; e.g. Yahoo Pipes or a Kinect sensor.
Also consider that your iPhone is a data centric device. You have contact lists, music, information about network connectivity, the camera and microphone (as sources of input) and more. What could be some useful ways to implement this data?