http://twitter.com/whitehouse/ (started May 1)
That's in addition to their other accounts:
http://facebook.com/whitehouse/ (started April 10)
I'm barely keeping up.
Update: I just saw this graphic:
Click to enlarge.
Newspapers are struggling, aren't they. When I grew up, it was all about newspapers, and a little radio. Television didn't come into play until I was a teenager. Even then, there was just one "Nightly News" broadcast, and if you didn't catch it for the few minutes it aired at 6:00 p.m., you were in the dark until the next day.
Newspapers, on the other hand, published several editions a day. Our Philadelphia Bulletin ran a morning and evening edition, at least that. Editions printed later in the day (and so with fresher news) were designated by more stars. (I think I recall papers with 4 stars, but my memory is fuzzy.) Newspaper carriers would walk the beaches in South Jersey during the summer, with huge canvas sacks slung over their shoulders, calling over and over, "Philadelphia Evening Bulletin, Bulletin here!"