We use http://google.com/ but http://asp.net/
also comes to mind.

ere:
!> what I want is web sites where I can see lots of examples,
!> different design styles, color combinations etc etc.

Start here : http://www.freecsstemplates.org/

There's 304 free CSS templates you can browse there.

After you're comfortable with CSS, and arrive at a decision regarding which template
you will use as the basis for your site, and adapt/refine it to your taste, you can work
on programming the site.

re:
!> Sites where I can see professionally looking UIs from usability point of view.

Usability is an entirely different issue.

Usability has more to do with which options you present to your users,
and having a logical flow of information for your website's business goal
so that your users don't have an experience which tires, or bores, them.

When information flows in logical, easy, steps, even if there isn't
too much "eye-candy", your users feel like the site has usability.

Juan T. Llibre, asp.net MVP
asp.net faq : http://asp.net.do/faq/
foros de asp.net, en español : http://asp.net.do/foros/
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