Options are Garmin MobileXT
(info) or TomTom has a mobile version, but they didnt put out a US version in its latest version, so you have to buy Western Europe and then an addon for the US/Canada. Price was in GBP and was 90 for the app and 20 for the US map. I have also used iguidance in the past as well. I preffered the interface on Garmin MobileXT, but without hacking, you are stuck with all the maps on the 2gb card and cant put them on a larger card. Iguidance will allow you to, but you have to buy the card from them and the max they have is 8gb. Looks like $100 for the maps on a 8gb card. Also may want to look at Route66 as they did some WM nav software in the past.