Opera  developer tools - http://dev.opera.com/articles/view/opera-developer-tools/

How to make opera use less memory - http://www.theprohack.com/2011/03/how-to-make-opera-consume-less-memory.html

A blog entry guide how to use opera sdk on mac os x - http://www.babilim.co.uk/blog/2005/11/building-mobile-ajax-with-os-x.html