City of Heroes Now Free-to-Play!
One of the best MMOs out there in my opinion. A much better superhero MMO than DC Universe Online and Champions Online, although it is quite old.
It uses the same 'freemium' model as most free MMOs out there. If you purchased the game in the past then you automatically qualify as a premium member as long as you use the same account.
'Justice' is the unofficial Australian server.