From the current home of Dungeons & Dragons comes this free starter for young people.
(From the download page)
Dungeons & Dragons for ages 6 and up - To help promote their upcoming novel Monster Slayers, Wizards of the Coast has put together Monster Slayers: The Heroes of Hesiod, a stripped-down version of Dungeons & Dragons that's fast, fun, and playable by adventurers as young as six. Best of all, it's completely free!
Reviews have been mixed but being free it gives someone a chance to see what all is available-and it is free :)