Ask HN: Taking HTML/CSS skills further: from websites to apps. How?

I'm pretty skilled with front-end work however there's a huge difference between making regular websites and making desktop-UI-like applications, e.g. Grooveshark.

I have trouble building applications with fluid UIs that resize as the browser window changes. Does anyone know of any books, information or guidance about these kinds of skills? Advanced front-end work, basically.