I went through the iTunes store, reviewed and captured most of the applications that in one way or another incorporate location awareness. There are a range of apps that are borderline cases. Indeed, for some it’s marginal and not central to the application but in other cases it’s what the application is all about: e.g., Yelp, Where, Whrrl, Loopt, Eventful, Urbanspoon, etc.
By my count about 10% of the apps had location as a prominent feature of the offering or proposition. But we’re really at the beginning and should see many many more location-aware applications for the iPhone in the near future. All the major players online will likely develop them. For example, there’s only one real estate app that I could find. I would expect Trulia, Zillow and the like would all have one, and so on.
If you want the overview document, you can download the pdf file here (it’s a big file).