It should start sometime in May - havent seen any of the big registrars offering it yet.
A german co is already offering prereg but cant be official. Probably they are just collecting prereg fees to have some income.
This from info site:
SCHEDULE: Scheduling details will be announced later in April. In general:
The list of available names will be sent to registrars in late April, 2002.
Participating registrars will then take name requests from the public. Registrars can submit their names to the registry queue.
Names will be awarded in June 2002.