title: What work has been done on cross-platform mobile development?
body: <p>Have any well-documented or open source projects targeted <code>iPhone</code>, <code>Blackberry</code>, and <code>Android</code> ? Are there other platforms which are better-suited to such an endeavor ? 
  Note that I am particularly asking about client-side software, not web apps, though any information about the difficulties of using web apps across multiple mobile platforms is also interesting.</p>