This has the possibility of bootstrapping a host of location aware applications :

This project exists to create a "open source" database of postcodes - and they even have a iPhone data collection application! Smart!

Ah - a GPS based Cat Tracker for those who want to know where their cats have spent the last 24 hours (or more for that matter) - and plot it on a map:

A small but powerful receiver was sourced. It contains a SkyTraq Venus 5 chipset. You can buy it here.

This is a idea I like - a full screen "wall" of messages for either a place or a group of people :

(Click for larger)

The first serious geocaching application I've seen on the Appstore - and it looks good. It does *not* display any navigation aids as such (i.e. a compass rose or similar) but read the FAQ for why this is not included (one reason is that the author has not mastered the graphics on the iPhone well enough - so 10 points for honesty!)