Limit By Domain von SamuelReed

Set limits for how many pages you can visit per domain. Doesn't block the homepage of that domain, but limits how many sub-pages can be visited per day. For example limit yourself to 5 YouTube videos per day, or 10 Reddit threads.
Now includes Reddit-specific features to be able to block the homepage and subreddits but still allow visiting specific threads. Useful for when the answer to your Google search is inside that one Reddit thread.
I wrote this purely for my own personal usage, but if anyone else finds it useful then great.