1. RhoMobile – This is an open source framework that is ruby-based. It helps you build native apps that run on iOS, Android, Windows Mobile, RIM, and Symbian devices.
With RhoMobile, you need to write code just once for all major operating systems. RhoMobile makes use of all your Smartphone’s features and builds the perfect cross-platform application.
6. Whoop – Though Whoop cannot be featured among the top tools used for cross platform app development, it is nevertheless quite an interesting framework. Even a developer who is not trained in the app development would be able to use Whoop to publish cross platform apps. Actually, Whoop is the ‘tool for non developers'.
The Whoop Creative Studio uses the WYSIWYG editor to allow dragging & dropping of mobile app elements while designing applications for Windows Mobile, Android, BlackBerry, RIM, and iOS.