MacNN cites the first user report of Mac OS X 10.4 (Tiger) shipping from the online Apple Store.
One user's shipment confirmation for the product places it for delivery on April 25th, 2005 via Fedex Ground.
Mac OS X 10.4 was officially announced on April 12th and the official worldwide launch is to take place on April 29th.
Update: At least one user has received Tiger, and the final build is confirmed to be 8A428