For anybody that has pre-ordered the game on Steam, you should go ahead and pre-load now, so that you can unlock it tomorrow. Steam has also just released the preload of the Multiplayer portion of the game as well a few minutes ago.
If you log into steam on their website, and go to the Call of Duty Black Ops page, it will tell you how much time is left before your copy will unlock.
For Eastern Time the unlock will happen at 10:00am EST.
