Galileo iOS app provides you with the most detailed and easy to use offline world map for free.
App allows you to record your GPS tracks and save interesting places you love as bookmarks on the map while traveling. It is also possible to share your itineraries with friends via Twitter, Facebook or Email.
It has pioneered the use of the advanced OpenGL map rendering engine which makes maps looks great at any zoom level.
Available on the App Store for free: http://appstore.com/galileoofflinemaps