http://www.finalfantasyxiv.com/anniv.../na/index.html
The above shows all the stuff they're doing for the anniversary, personally I'm most excited for the return of the cross over events, as I never finished farming all the weps for Lightnings and now I can do the Dragon Quest and Final Fantasy 11 events.
I was a little surprised at all the stuff they're doing, but I do like that they're making a fuss of the game, especially since it seems to be doing well.