The Windows Phone app which has gone free next as myAppFree app of the day is Metro Maps.

Metro Maps Details:

Would you like to have all the famous metro maps in your hand? If you like travelling abroad you will not always have an internet connection. This app is just for you.
The database is constantly updated. We are always adding new maps!

This app works offline. You only need to be connected to the internet the first time you use it.

Install Link