I have to present a prototype of an web app in the following days to one of my clients, the thing is I\'m not so good at CSS and worst of all I\'m almost never happy with the re
I can't believe nobody has mentioned:
http://www.extjs.com/
Its a commercial js frameworks, but pretty affordable, and makes putting together a nice UI a breeze. There's a much more complete set of elements then jqueryui, and its designed to make an entire app. I've only played with it a little, but I really love it so far. Free for personal use.
If you really want to get a feel for a complete UI developed with EXT, try this url:
http://docs.sencha.com/extjs/4.2.1/extjs-build/examples/feed-viewer/feed-viewer.html