Yesterday, Apple annouced that pre-orders would start at 1 AM PST but it seems like you are able to order an iPad 2 now! Go order one now 🙂 ! Estimated shipping date for iPads are from March 18 – March 25th.
Online orders will ship within 3-5 days, and you are currently limited to two units per order.
Update: Apple has extended shipping estimates for new orders out to 2-3 weeks for all 18 models