How to Program the BlackBerry With J2ME

An excellent article describing Blackberry architecture and two application models (The browser-based model or Custom Java Application).

The browser-based model allows developers to focus on developing back-end content in a standard markup language, such as the Wireless Markup Language (WML) or the compact Hypertext Markup Language (cHTML). Using existing browsers’ client capabilities frees the developer from worrying about the client interface – but it does limit client functionality to what the browser provides, and there’s no support for offline processing.

Custom Java applications enable developers to develop customized user interfaces and navigation, and support content beyond text and images. Developers can also build applications that users can download and install on wireless devices, so they can continue to use offline capabilities while out of wireless coverage. Several BlackBerry devices come with a complete set of APIs and tools that enable you to build custom Java-based applications.

It gets you started developing applications and deploying them on the BlackBerry. If you are developing in Java for mobile devices or interested in this area, you would very much enjoy it.
Very good article with excellent coverage. Read it here.