I think Taxi Book iPhone app is very useful and well done.
I want to tell you a little story about how I got introduced to Taxi Book iPhone app. I am just arrived in Chengdu; the first day I went to a Carrefour near my apartment to buy some stuffs for the kitchen but unfortunately there were no the things that I was looking for.
So the first foreigner that I run into i asked him “do you know if there is Ikea in Chengdu?”. He replayed me “I don’t know but I can check on my iPhone”. And in a few seconds he told me the address of Ikea in Chengdu and all the information to go there.
He said to me he was using a new application for iPhone call Taxi-Book that help you get around the city.
The same day I bought it on the iTunes website and I have used it a lot. It inform you also about the GPS coordinates and if you want you can also add other locations that you have discovered. I find very useful the fact that all the addresses are organized by category.