If you go to the Nikonusa.com site, and click on the "where to buy" link on the D100 page, you will receive the following message:
D100 Digital SLR deliveries are scheduled to begin June 28. Information about authorized dealers will be updated as deliveries begin and on an ongoing basis. Please check back.
A couple months ago, I placed a pre-order for a D100 with my local camera shop for a deposit of $200. They expect to begin receiving the cameras tomorrow, but it is unclear how many of them will be available.