I wanted to do up an article about making your own ring toss game that would knock your socks off, but I can't beat this great tutorial. It's a straightforward process of taping together empty water bottles.
For variations, you might put a little sand or rice in each bottle, or even colored water. It might be fun to use different sizes of bottles, with some bottles being worth more points than others. Of course, this would also go nicely with a lesson on recycling. The kids themselves could drink the water, and then you could talk about ways to reuse the bottles.
Start drinking that water so you can "toss" together this fun activity! (Sorry, that was bad. It's been a long week, okay?)