android actually has a native development kit that only requires you to use java as a loader.
can be found here:
http://developer.android.com/sdk/ndk/index.html
wise option for ports would be iOS (iphone/ipod touch/ipad) and android (desire, galaxy s, galaxy tab, x10, countless others) as they are both now becoming the most widely used mobile platforms. though a windows mobile port would be something that people would use.
sdk's for ios and android both come with pretty good emulators too, so cuts on the costs of actually buying a device.