Well...trouble with those is that in general, I would have to take them to it. I'm hoping to build something that they can get to on their own, eventually - put in a dog door and such. I did some talking here yesterday and with my brother last night, and I think what I'm going to look into is putting in a sort of "play yard" - not fence in the entire yard, but just the corner of my property that runs from the side door to the front right corner of the house as you're looking at it:
Just that one corner, see? It would be a decent size (as I've said before, this picture makes the yard look a lot smaller than it is, I suppose because it's flat), and I could put a little gate at the end of the path that runs from the door to the road (not really visible in the picture, but it's there!).