Here is one of the [tag]baseball fielding drills[/tag] that I started using a couple of years ago. It works on the fundamentals of fielding the ball and conditioning.
Start the line at home plate and one player at either 1st or 3rd (this player is cut-off for fly ball to outfield).
First player runs about 30 feet turns around expecting a line drive from coach, throws it back to coach or next player in line. The same player now runs another 30 feet and turns around expecting a ground ball and throws it back to coach. Now another ball is thrown to the outfield and she has to track it down to catch it and then throws it to the cut-off in a relay to home or 4.
The rotation I use is–once the player has got the fly ball and has thrown it in, he now becomes the new cut-off player and the cut-off player goes to the end of the line.
I have done this [tag]baseball[/tag] drill with 1 or 2 lines. It can be done on a field or in the grass if no field is available. I have also used it as a competition to see which line can get done first without missing the ball and good fundamentals.