The HTML5 Mobile App Framework known as Sencha Touch looks extremely promising. After visiting the examples on an actual mobile device (check Kitchen Sink) I was entirely convinced that this is worth bookmarking, reading up on and diving into for any future mobile development. The writeup's are enough to get excited over but there really isn't anything better than just seeing it in action - try out the Solitaire game in a WebKit browser and you'll see what I mean.

Heads up via Daniel.