Disney released PotCO a few weeks ago. i played a bit to see how it was.

Pro:
[LIST]
[*]Free download and free-with-ads playing make it affordable
[*]Mostly family-friendly experience. definately an MMO you could play with kids 8+
[*]Very friendly players, no foul language from my experiences
[*]if you do pay, the pricing is excellent ($5 first month, $10 each after)
[*]Sailing is a hoot, group up and go blow some ships out of the water
[/LIST]

Con:
[LIST]
[*]only way to cancel paid-for version is to call them up. (i called and complained about this one)
[*]Getting places by yourself can be a real pain.
[*]Serious restrictions on skills/Guilds for free accounts
[/LIST]

if you like Pirates, enjoyed the movies, and want something free to cheap, you might like it.