What iPhone maps app can I use if I don't have a SIM card? I'm going to be using my iPhone overseas without a SIM card, but I want to use turn-by-turn navigation to walk and drive around.

I'm willing to plot my route via wifi before I leave the house, but I won't have internet because my phone won't have a SIM card.
Navigon
TomTom
CoPilot*


Navigon offers different apps for worldwide coverage.

Depending on where you are headed TomTom has several different apps for particular regions. Scroll down on the iTunes page to see some options.

*It appears that CoPilot offers directions when offline, but not turn-by-turn directions. 

On all of these apps be sure to check and verify that they provide maps for the country (or countries) that you will be visiting.