Hokie,
You have gotten some good responses and advice so far. I have the original Cannon Rebel digital camera. The camera is pretty good for sports photography especially when you consider the price. A couple things you might want to consider...
How many pictures per second do you want to be able to shoot in a burst? My Canon is the older version and it only shoots about 2-3 per second. This isn’t a terrible frame speed however if you are wanting to take a series of sequential shots of your son pitching, making a tag or batting you may not catch everything. This may have changed for the newer Rebels however for a little more money you can upgrade to something like the Canon 30D which justbaseball mentions that gets I believe around 5-8 pictures per second in a burst. In most any baseball situation I would think this would be more than enough. For a novice photographer (which I am) I have found that shooting in burst can make up for missed timing and help get a great shot. That’s the beauty of digital photography; you can take a lot of shots and delete the ones you don’t like.
Second thing to consider is how big a telephoto lens you will need. I have a 70mm-200mm which works great to take pictures of my sons. (They are primarily pitchers and infielders) however when I take shots of the outfielders it still looks like a long-range shot. So if your guy is an outfielder or cather (taking straight on shots from the outfield) you may want to look at a longer zoom. You may also want to look at the "f" rating (i.e. 2.5 or 4.5) of the lens. This makes a big difference if you are hoping to shoot any sports indoors. I will not even try to explain this however it is something you might want to ask your camera retail guy about.
Like I said you have gotten good advice however if I had to do it over again I would have gone with a camera that had a faster frames per second and larger telephoto lens. Now that I think of it, maybe it's time to talk to my wife about letting me upgrade. Anyone want to buy a good used camera!
Good luck and enjoy!