kudos, dictionary.com

It's about time - dictionary.com has finally revised their UI, and went from 2 out of 10 to 2.0. They still have pop-ups, some residual ugliness, and way too many ads, but hey, that's what you get for free. Their "Cite This Source" is totally sweet, by the way - wikipedia needs that.

Still, for my money, nothing beats UrbanDictionary.com.