I ended up creating a repo with blacklist.txt myself and will add to it for my own usage. I don't see anyone else who'd maintain this. Feel free to use it / contribute to it.
* code-search-blacklist based on this jhchabran's repo [1]
* pinterest.com based on SwiftOnSecurity's interesting seo analysis [2]
Maybe your repo could be an opinionated list of things developers find annoying about google search results, where others might value sites like pinterest in their results.
[1]: https://github.com/jhchabran/code-search-blacklist
[2]: https://twitter.com/SwiftOnSecurity/status/12588753334467174...