My personal favorite is https://bravenewcoin.com/events , which generally has all the events from listings to conferences to coin burns, but I personally think most of the websites just copy-paste all the events from coinmarketcap website itself, because you won't find any additional events in different calendars, generally, they are all the same. You have asked this question in Trading discussion makes me feel you are going to make trades based on the upcoming events, I personally would tell you to avoid doing it, it can be highly deceptive, as a layman it's difficult to predict which event would trigger what thing for that coin.