Ask HN: Which websites actually have a useful search that Google can't beat?

Everybody uses Google, Bing, DDG, or some other search engine. But are the search giants as ubiquitous as they seem? I think there's a great value to individual sites' search features, mainly because they go beyond the grasp of GoogleBot.

There was a post recently about Google's main competition being Bing. I think that's entirely untrue. I think their main competition is the long-tail of search that they simply don't have the dataset to compete against.

Here are sites that I can recall using the search feature, and it actually being useful:

  - Wikipedia (half the time I use Google, though)
  - SearchYC 
  - Urban Dictionary 
  - BTJunkie 
  - StackOverflow
  - Delicious
  - Twitter
  - YouTube
  - eBay

What sites do you find have a useful search feature?