National Oceanographic and Atmospheric Administration
In my opinion, the "MOTHER OF ALL WEATHER SITES" - informative, user-friendly and quick-responding. Radar loop updates every seven minutes - a great feature for those in areas prone to rapidly changing weather conditions. Not aesthetically or graphically wonderful, though. Hey, their specialty is rain, not art.

JJill catalog
Very cool and visually appealing. I love the font that's there now. They are always coming up with new graphics and inventive ways of presenting their products, like having a catalog that allows the user to actually turn its pages using a "next" button. But the basic functionality always remains intact - no new learning curve each time you enter. Nice clothes and good sales, too.

CNN
For a quick scan of the latest news, I particularly like the bottom of the home page where the top stories are organized by category.

USPS.com
What can I say? I'm a homer! But I really do use it quite frequently, both personally and professionally, for zip code lookups. I think it's a hidden jewel, especially for small shippers, like ebay sellers. Occasionally, the "Locate a Post Office" link doesn't seem to contain the most accurate information. But I guess that's to be expected when you need to keep up with over 50,000 of them!

USPS.gov
(Link is to a "print screen" of the homepage - public cannot access this site, as it is behind a firewall)
A recent redesign, it replaces a confusing and overdone (too many large graphics with text superimposed) home page. I am appreciative of the new design's simplicity.