EggMaps HD is an iPad-only app, which provides Google's Maps utilizing the iPad's full screen (rather than just running the iPhone version of Google Maps).
To see the difference visually, check out these images.
Picture of Google Maps for iPhone running on an iPad
Picture of EggMaps HD
EggMaps HD is free in the app store today.
See the app store page for more info (click the big egg above).
A new release is coming very soon, which adds the ability to drop markers and improves street view usability.
I assume you still need wifi/3G/4G to download the maps?
Is there any app that has maps built in and you can just use your GPS and navigate?