I want to develop a mobile version of an existing web site, so which platform/SDK will be most suitable for Blackberry and Nokia smart phones? Secondly, which approach will be my best bet - native app or mobile web app?
I use jQuery Mobile. So far I'm very satisfied. You can check details at http://jquerymobile.com/
It has a full support for Blackberry, Nokia Lumia, Nokia 950 and N9 (Meego 1.2) smartphones and enhanced experience except without Ajax navigation features for Symbian powered Nokias.
Besides that, it supports all modern mobile browsers, Android and IOS included.