The website for Black Ops 2 has been released, and was accessible here - http://callofduty.com/blackops2/ (http://callofduty.com/uk/en/blackops2/ for UK residents), until being taken down shortly afterwards.
Currently, it has a page for the reveal with a video player, however the video player is not working yet, and the URL of the YouTube video it is supposed to play (http://www.youtube.com/watch?v=upCWKsa9Skw) is currently private. It seems that that URL will eventually display the reveal later tonight.
There is also a listing for an "interactive trailer", as well as a page for images, though no images currently are available.
Note - the site doesn't seem to be working for some people, try the UK site if the standard one will tell you that your IP is blocked.
Note 2 - the site is currently inaccessible, it will probably be accessible after the reveal.