Oh, good idea.
Sozlet is currently heavily into Webkinz. I mostly approve.
Basically, you buy or are given (she was given the first one) a small stuffed animal that has a tag with a code in it. The code gains you entrance to Webkinz World, where you can do a whole lot of fun stuff. Mostly you take care of your animal (feed it, bathe it, make sure it gets enough sleep and exercise, etc.), and earn money in various ways to buy things to enable you to take care of your animal (food, bathtub, bed, trampoline, etc.)
What I like about it is that the site is nicely put together, with a lot going on and a lot of it at least a little bit educational (especially the money-management issues -- too many decorations for the house, no food for your Webkinz) and that the toys are really reasonably priced. (~$9 for full-sized ones and ~$7 for little ones.) The idea is that you collect a bunch of them, I think, but she has two big ones and one little one (a family) and is content, so that's not a lot of money for something that she's enjoying a lot.
The stuffed animals are themselves cute and cuddly, too, the whole family has joined her in her bed and often when I wake her up in the morning the littlest one is tucked under her chin.