The iPad will ship in the United States on April 3 but a lot of the associated accessories will not be available on launch day if the online Apple store is anything to go by.
As noticed by 9 to 5 Mac both the iPad case and iPad keyboard dock have slipped past the iPad ship date with the latter accessory not available until "May".
It is unknown why the iPad accessories have become so delayed but speculation points towards high demand as the culprit.
[Update 16 March 2010 23:00 GMT] Apple has adjusted the shipping window for the iPad keyboard dock to "Late April", not a far departure from "May" but an improvement.