I was in the midst of researching a couple of these different home screen launchers, but alas, Lifehacker beat me to it. They have a very through comparison of 3 great home screen app launchers.
If you are looking for something better than what comes on your Android device, take a look at the Battle of the home screen launchers. It will let you see how 3 of the many possible choices work. Most of them can do more than give you a different look or additional screens.