@andybaio

It's software, not a site, but DEVONagent can work like this. It's intended to be a research tool, and you can do extensive web searches and tell it to ignore sites or entire domains or whatever you want. I use it instead of any of the usual search engines when looking up, say, a movie title that I want to write about on the blog. I only get 'worthwhile' results now that I've trained it (which didn't take much effort or time). → https://www.devontechnologies.com/apps/devonagent

There's a lengthy free trial.