When I originally drooled over, and finally received my Nokia 6600, Niska as I affectionately refer to it (bonus points if you know the reference) I had high hopes for its hackability.
Fortunately, very smart people, and Nokia, got behind deploying a Python intepreter for Symbian, which makes rapid prototyping & application development easy and fun - if you know Python. Which I now kind of do, but am no expert by any means.
Yet again, smart people have convereged and this time they have presented to us Ajax for mobile platforms via Opera. This type of framework will allow for very simple, and rapid development and deployment of web, and standalone applications for mobile devices. Mapping, photos, contact lookup, wikipedia, local databases, chat, etc. etc.
Of course, this is a brilliant way for Opera to strenghten its Mobile market share (which it obviously is focused on, after giving their desktop version away for free) - kudos to them for providing the community the means to write software for them.