Investigative reporters who are looking for White House visitors more embarrassing than socialite gate-crashers will find a new tool from the Sunlight Foundation handy.
Half the battle was won when the Obama White House started releasing its visitor logs. But the information there — in its raw form — leaves few clues about who the visitors are and why they are visiting.
The Sunlight Foundation — the cyber-gods' gift to gumshoe reporting — has compiled all the logs into a database, and then linked each name to a series of background resources and search engines. This makes it easier to know who the visitors are.
See the online searchable database on Sunlight's site. 
So far, only September 2009 data is up. But more is coming. Standard warnings apply: verify visitor identity independently before using for publication.