There are several hitting aids available to ballplayers nowadays, other than batting tees that are very nice and should be taken advantage of. The first of which is the soft toss machine. These are excellent because they allow you to work on your swing in a space as small as your garage all by yourself.
The Jugs Company makes one that appears to be very nice. It sits on the ground and tosses the ball toward the batter every five seconds. It runs on a rechargeable battery so you don’t have to mess with an extension cord or an outlet. At the time of this writing, the price on this machine is $235.
There are also a few other manufacturers that put out a different style machine. This style consists of a tripod-like stand that holds a rack of baseballs. At a set interval, the machine releases the ball and it rolls down a shoot which tosses the ball toward the batter. These are also very nice as I have owned this style of machine. They usually will run anywhere from $100-300, depending on the quality and durability.
Other than soft toss machines there is another style of hitting aid, called the Hit-A-Way, that allows hitters to work on their swing and timing while hitting a ball. This consists of a cable with a ball attached and rigged onto the rope. The rope can attach onto a basketball post or tree. Once attached, the rope can be wrapped around the post and as it unwinds, the ball will revolve around the post and bring it right through the strike zone of where you’re standing. As you hit the ball, it will wrap around and unwind again allowing you to get numerous repetitive swings in. Check out the YouTube video below to see it in action. These are usually cheap and cost less than $50.
You'll also need to make sure you've got a good soft toss net to hit into while using the tee or taking soft toss. There are several of these models to choose from.
Another style of hitting aids are mechanisms that help you stay inside of the ball as you hit it. To "stay inside" means to not roll over the hands on the swing until contact is made with the ball. This helps you to make more solid contact with the ball, as well as hit to the opposite field. The devices are made up of a sort of cable that connects your wrist to your upper arm on your lead arm, preventing it from extending too early in the swing.
Something that I have never tried, but is available are weighted batting gloves. The idea with these is to improve wrist and forearm strength which in turn will increase bat speed. Give them a try if you want, but I cannot speak personally if they actually work or not.
Ballplayers should take advantage of as many of these hitting aids as possible to help improve the fundamentals of their swing. Remember, regardless of what device you are using, the idea is to develop a short, compact, but powerful swing, and always work on improving bat speed.