http://www.battle.net
In Blizzard's Battle.net website there is the intro page that reads 10 7 05.
In the background every refresh loads a new picture, there's an Orc from Warcraft, an Elf from Warcraft, characters from Starcraft, someone said that even a Diablo related pic is there.
So what could the Big Announcement be?
Starcraft 2? Warcraft 4? Warcraft Adventures? Diablo 3?
I guess we'll know in a few hours...