Well i was researching that area but it is very frustrating how there is no approved universal platform for all cellphone operative systems.And what is especially frustrating,you cant even develop native apps for iphone unless you own mac.You could improvise by using HTML 5,java or jquery mobile which working on all platforms,but such apps probably wont be accepted on apple/android/microsoft store.Also i hate monopoly of stores,you cant even publish internal app for you own use without their approval.
And here is some url's which i found about developing:
http://xamarin.com/
http://www.mobiaccess.net/developers
http://www.applicationcraft.com/pricing-main
http://phonegap.com/