in March, I posted up some links to some tools that would allow you to develop native apps for iPhone and Android using only web technologies:
Here's that post:
However, I have since learned that you can do the same in Symbian nowadays (since April):http://developer.symbian.org/main/tools_and_kits/symbian3_developer/index.php
and also, that's the way Palm do it in general for webOS:
Needless to say, if I had the time, I'd be creating tonnes of apps, instead of just thinking about it...