A video posted over at Mutants and Magic shows Peter Cushing playing with his toy soldiers "according to the rules laid down by H.G. Wells in his famous book Little Wars." How's that again? While probably very old news to serious wargamers, I didn't know about this... I've only just perused it but already see two great things going for it - it's rules light and in the public domain. You can download it from archive.org or Project Gutenberg. There's a short companion text too.
Have any readers actually played this? It seems like it might be a great introduction to the hobby for kids.
Of possibly related interest.