We made a little outdoor seating area with a fire pit and then realized we needed to figure out how we were going to fuel it. Plenty of downed trees around us, but we came to realize that logs didn't burn well unless they were split. I did not trust myself to start swinging an axe around and went looking for alternatives. I found this and gave it a shot.
We got the King/XL model which can accept a 9" piece of wood which is most of the pieces we would want to use in a fire pit anyway. It is an incredibly simple setup, basically a solid cast iron rig. You place the log standing vertically in it with the end on the wedge. Whack the other side with a hammer until it splits.
The thing is actually a bunch of fun to use, and they're not kidding when they show kids doing it. My little one loves to whack the log with the hammer once I get it started and stable, and she is capable of really splitting it on her own power. She won't crack a full on log, but anything smaller succumbs to her mini-might :-)