Haven't looked into it, but supposedly with BB6+ you can make apps with HTML5/JS. I switched back from iPhone for the bold 9900. It's come a long way.
Also, definitely worth a look is bbUI.js (https://github.com/blackberry/bbUI.js/). It's still very much beta, but RIM are doing a lot of the UI hardwork for you; without it you end up with a white screen and have craft the UI yourself. It's a bit like jQTouch for BlackBerry.