Everyone would like to see their baseball players hitting the ball harder. Quite often, youth batters get so anxious to hit the ball that they end up way in front of many pitches, with their weight too far forward and/or their bodies in awkward positions - both of which rob leverage, and thus power, from their swings.
Timing is another issue for another drill, but a quick and easy way to teach players to keep their weight back (and therefore keep their optimum balance and leverage) is to have them hit an old, deflated basketball off of a tee. Turn a toilet plunger upside down and place it in your tee, then place the partially deflated basketball on the tee.
Make sure that your hitters set up in a proper batting stance - don't let them cheat or get lazy, or you will minimize the positive impact of this drill. Players will discover that they must keep their weight back over their back foot in order to hit the ball off of the tee with any authority. As a bonus, the drill forces a good follow through, as well.
This drill is emphasized by many a successful coach; if you don't really have the time (or space) to devote to long batting practices (which can be of questionable value, anyway), try having your guys hit an old basketball. I have read of coaches that use this almost exclusively in terms of batting practice, with great results. One thing I guarantee is that prudent use of this drill will turn those infield dribblers into solid contact, and solid contact into scorching line drives.