free open source "Meet Tux the Penguin"
Educational Software
Tux Paint
Tux Math of Command
Fun Games:
Tux Racer -- great game, but note that it doesn't run well on older systems.
Super Tux (Super Mario clone)
Icebreaker (xonix clone)
PDF Print-outs:
Tux Origami, 
Tux Buttons (or stickers)
Also
Plus a short lesson on operating systems, Tux and open source, including direct links to Wikipedia sources.
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