Can't think of the names of these exercises so will have to explain it to you.
Line everybody up in two separate lines, put cones out infront of each line. Throw the ball, make them go through the cones pick the ball up, spin a and launch it back in as fast and as accurately as they can before throwing it for the next person. It is a good workout because of the speed of it, it is competitive so makes people work harder and if you close the gap between the cones you can improve footwork while also working on the picking up and throwing the ball part of fielding.
The other one is to line everybody up with one person with a bat and maybe a glove(Depending on how hard you want the throws to be) on the other side of the hall. Batter hits the ball on the ground, first person stops it up and throws it back to batter. Batter hits ball into air this time, the first person catches it and launches it back before going to back of queue and next person goes etc.
Both decent workouts for fielding.