A very difficult play for outfielders is charging and catching a screaming line drive. Depending on the spin of the ball, the ball may dive, sail, or even knuckle. As an outfielder approaches a low line drive, it is often advantageous to slide to keep the ball closer to eye level.
To execute this drill, the coach takes a knee with a bucket of balls directly in front of him. The outfielders are lined up about 30 feet out in front of the coach. On the coaches 'go' signal, the first player sprints to you and begins a slide (to your side), just before they reach you. A slide here is identical to a slide into a base... feet first with one leg tucked under. As the player begins to slide, the coach should toss a ball into the air (straight up, 2 to 3 feet) to your side. The player is then to slide underneath the ball and make the catch.
Certainly, you can take this drill and make some variations to make it more difficult for older athletes. We make this drill a little more fun every once in a while and wet the grass so the players will slide longer and faster.