http://www.quora.com/

http://www.facebook.com/

http://www.delicious.com/

http://www.yelp.com/

http://*.google.com/

All these sites have interfaces that are largely composed of text, borders and shaded backgrounds on a white canvas. There's a distinct lack of gradients, rounded corners, drop shadows, background images, fancy buttons and oversized text fields. They don't necassarily look pretty but they're not ugly either (I'd put reddit, ebay, craiglist under the later category). They also work rather well from a usability perspective.

Having virtually no design ability, interfaces like these appeal to me. What other sites have a plain front end and good UX?