You never know how great something is until you become an avid user. I have installed several of the Tux programs at schools, but this last week I installed Tux Paint at my house. My kids love it. There is nothing better than seeing a three year old turn on the computer click on the Penguin and start "painting." Not only is this allowing kids to be creative but its teaching them fine motor skills to use the mouse. It is available on all three major OS's Linux, Mac OS and Windows. Like all open source programs its Free!
Tux Paint: Computer drawing program much like KidPix without a price tag. Make sure you download the Rubber Stamp collection too. It gives you ten times more options for students to use.
Tux Math: Did you ever play Missile Command as a kid back in the 80's. Tux Math takes that game concept and combines math skills for a entertaining and engaging game.
Tux Typing: The penguin is hungry and has to eat but the only way he can eat is if you type the correct letters as the fall from the sky.
As with all Open Source programs the only way they can survive and pay for server space is for you to donate.