We use this drill at the beginning of the season. It gives players a lot of reps at fielding ground balls and fly balls. It is a great drill at the beginning of the season as a judge to see which players are outfielders and which are infielders.
The drill requires two fungos, one on the first base side of home and one on the third base side of home about half way between the bases. The drill works best with 10 players. Each fungo has a shagger. Align four players at the infielder positions. The other four players should play outfield, with a LF, LCF, RCF and a RF. The 1B fungo hits ground balls to the third baseman and shortstop who return the ball to his shagger. He then hits fly balls to the LF and LCF who relay to the 3B and SS respectively. The 3B fungo hits ground balls to the 2B and 1B who return to the third base shagger he then hits fly balls to the RCF and RF who relay to the 2B and 1B respectively. After three reps the players rotate.
The 1B becomes shagger for the third base fungo, while the 3B shagger moves to LF. The RF becomes shagger for 1B fungo, while the 1B shagger moves to 3B. All other player rotate to the position on their left.
If you have more than 10 players this is also a great time for you to have your pitchers and catchers working off to the side, out of the way of badly thrown balls.
This can be a little dangerous if not done with caution since two balls are going at once, but it is a great way to evaluate the players and the rotating keeps them from getting bored.