The White House Blog announced they will start posting a list of all the visitors to the White House. A small group of guests will not be listed due to national security.
Unfortunately, due to legal pressure via lawsuits, it took this long. The president campaigned on transparency and he has not followed through. The White House finally gave in and settled with terms from the lawsuits.
You can research further details on information and technology at the Office of Science & Technology Policy.
