Simple website that quizzes you on the number of possible chess moves.
The hope is that this is good practice for board vision. Beginners at chess are often advised to consider their and their opponent's moves, and checks and captures in particular. The first step in this is noticing what these moves are.
You can also practice visualization by having it give you a few future moves to consider. Then you have to enter the counts assuming those moves have been played.
Misc note: all of the positions where castling or en passant are available have been filtered out already. So don't include these moves in your counts.
Thanks to Lichess for their open puzzle database and for generally being a great free website, and the user GnocchiPup on that site who explained the benefit of move counting to me.