Little Red Riding Hood maps well to RDF
After two phrases, the board was already full of triples about mothers, grandmas, the little girl, her hood, baskets, etc.
It's a fun example, and everybody knew the problem domain quite well, which helps. Students even discovered inference by themselves, mentioning that two "is mother of" predicates on a path imply an "is grandma of" predicate.
By the way, if you haven't seen Tex Avery's version of the story, you absolutely have to - it's incredible.