Just wanted to give a quick shout-out to Scholastic and Legacy Interactive for Zoo Vet (scroll down in the games menu and click Vet Games), a computer game that allows you to diagnose and treat ill or injured zoo animals. Marketed for ages 9 and up, the program works for both Windows and Mac, and could probably be handled by a very motivated 7 or 8 year old as well. Xavier (10.75) got the game for Christmas but just tried it out last night. I had to drag him away from the computer at bedtime and then again this morning for school. A review at Parent's Choice complains that there is not much latitude for experimentation, so he may finish the game quickly, but it's been a long time since he and Wolfie argued over educational software like they did last night.
Legacy also publishes "Vet Emergency" and "Vet Emergency 2", aimed at 6+ year-olds, available through Scholastic and through Legacy's own website.