It's a strange number, 61 (not like 42), but Google has a nice interactive Hitchhiker's Guide theme going on today.
Google missed a great opportunity. I typed in "Earth" and thought it may have loaded an "introductory gag" page that read nothing more than "Mostly harmless." Alas, no such humorous luck. Sincerely, Bill
If you keep clicking on the Guide, it shows you little animated scenes from the book. Very cute. I wish they'd made Marvin speak, though. It would've been great to hear him say something whenever you clicked on the door.