MapQuest released an application for the iPhone last week and it is awesome. The link at the beginning of this post links to the iTunes App page.
I really dig the application. The one thing that I really like about it, as opposed to the maps application that comes with the iPhone, is that it can mark the location of local points of interest. For me this is great because I just moved to a new area and I use it quite a bit to find restaurants. I am sure it can be used for other things too, like for instance, coffee shops or gas stations. It also includes a feature where one can turn directions in landscape view and flick through the directions as they menuever through the stages of their drive, thus acting much like turn by turn directions without the benefit of changing screens when the action is completed.
All in all it is a pretty cool application that I have been using in the place of the maps application for almost a week now and haven't had any regrets about changing, though I am sure with the addition of the compass, that the maps application is pretty cool right now.
If someone out there is works for MapQuest and is reading this, I hope you add the driving direction deal (map switching direction based on your direction of travel) into account when you release subsequent versions. I would also like to see some new Points of Interest added like Furniture Stores or maybe music stores or possibly even Historic Locations/Points of Historical Interest.
If you have an iPhone or iPod Touch and haven't already gotten this app, I reccomend you at least download and try it.