How to develop a mobile Apps that uses Offline Maps?

Actually there is. Its called Visual WebGui and they came out with a feature that can give developers the option to design applications that can tolerate adverse network conditions. In the event of a lost or interrupted server connection applications can continue to operate without post-backs to the server. Beyond dropped connections, Offline Mode can help keep your Visual WebGui application responsive in the event of a slow network connection, with changes requiring an internet connection being synchronized in the background. you should read their blog about this subject  

tnx Suthish sir, but I have to use an offline map. Used maps are get stored in cache and usable for few time without internet connectivity.

There is a requirement, where downloaded Mobile Apps will be able to use Geocoding and Routing without connecting to internet(here can't use cache) and for this Offline Map is required.

Someone suggested me to save the portion of map in SQLite and use, but how to wireup is not known yet.

The another challenge is this apps will hybrid & for different mobile OS. 

Long back I came across a third party tool (GMap.Net) which supports local caching.

If you are looking for Bing Maps with windows 8, refer...

http://social.msdn.microsoft.com/Forums/en-US/bingmaps/thread/6ec20790-1df5-4a6f-b022-a1b3d08a5586/

For Google Maps, refer...

http://www.markandey.com/2010/05/offline-google-maps-in-cnet.htm

Best part is all above tool supports .Net...