In Lonely Frogs of Wisconsin, you play a female frog looking for a mate. When you start, you're assigned a frog of a particular species, and shown a bunch of different species of frogs; mousing over them, you can listen to their mating calls.
Then, you select a particular type of landscape to explore (a pond, a wooded area, or a meadow). Mousing over different portions of the image, you hear natural sounds -- bird calls and other noises, but also frog calls. If you click on an image region, a picture of the frog calling from that region (if any) appears, but you also spend "eggs." Click too often, and your girl frog dies. Find her a mate of the same species, and she's no longer lonely, I guess. The game tracks "number of frogs saved," and encourages you to replay with a different species of frog.
From a game design standpoint, this is mildly interesting, because it's dependent on audio cues rather than visual ones -- and yet in other regards is very similar to the hidden object games that are currently popular in the casual game market, as inane as their basic gameplay may be.
I guess this is educational, if you want to know frog calls and maybe something about what habitats different frog species occupy. It's also, unfortunately, pretty dull -- the only really fun thing about the game is its name, alas. Still, it's certainly different.