June 6th as rumored this morning. The phone will go on sale nationwide (US-only for the moment) at Sprint stores, Best Buy, Radio Shack, and select Wal-Mart stores. The Pre will be available under Sprint's Everything Data or Business Essentials with Messaging and Data plans. Accessories include the optional $69.99 Touchstone charging dock kit that includes the $49.99 dock and $19.99 Pre back cover. June 6th, that's two days before the WWDC keynote. Poor Apple.
Note: Looking more info? Check out our giant Palm Pre hub!