I also think that mini games would be great. I know i loved spending time at the golden saucer in FFVII just because of that.
Everything from contests to competitions could be revolved around these mini games.
ie) Like a carnival of sorts... have dagger/dart throwing competitions with prizes, jousting, races (on dragons/griffons/horses or whatever), duels (computer controlled or PvP), magic displays etc.
But instead of having some events deal strictly with character stats, it could deal with actual skill (ex. dart throwing dependent on speed and direction of mouse movement) and in turn would allow for more involvement of newbies and veterans alike.
As well some mini games that deal with problem solving would also be cool. Again, this could be open to everyone in the game, and a prize could be given to those who solve the puzzle first.