I have found these baseball fielding drills improve fielding and throwing in the infield, moving to bases to receive balls and relaying balls from the outfield.
Infield Throwing Drill
Set your infield, even double up on each position if you want
The coach or assistant coach hits 4 ground balls to 3rd base player who:
1. Fields ball and throws home
2. Second ground ball is fielded and thrown to first
3. Third ball is fielded and thrown to second
4. Fourth ground ball is fielded and thrown to third
All balls are returned to catcher via first base. This is repeated for each position on the infield.
Coaches can apply penalties for any wild throws or missed fields or rewards for any player that goes through without mistakes.
Outfield Drill
Half the team lines up in Left, half the team in Center. Hit flies short and long between the fielders to teach the players to have one call for the ball, the other scoot behind to back it up.
If the ball gets by them both they space out to relay the ball back into second base, where the coach hits from. Even my infielders have also benefited from the drill.