/r/serendipity is an open source meta-subreddit redditbot created by Chris Dary. It is —

meant to broaden the perspective of its subscribers. It takes a popular entry from a random subreddit and posts it every few hours.

If you want to increase your exposure to niche subreddits, or just your perspective on things on the web in general, serendipity might help you do that. But it might not. It’s a bot, after all.