Unsurprised to see Paul Graham's home page among the top 10 most similar websites to news.ycombinator.com, but a bit surprised about xkcd: https://explore2.marginalia.nu/search?domain=news.ycombinato...
My toy, which relied on scraping <ul> and <ol> lists of people's favourite bands from personal websites, had almost nothing to go on by comparison. last.fm might have been able to do something good with the data they collected, but they seemed to die on the vine once they were acquired.