Engadget has just posted:

We just got the announcement, iPhone OS 3.0 is coming. Set your clocks, mark your calendars. It’s going down March 17th. Apparently, we’ll get a sneak peak at the new OS, as well as a look at a brand new version of the SDK.

Gizmodo has the text of the invite up:

Join us at an invitation-only event to learn about the new SDK and get a sneak peek at the iPhone OS 3.0 software. The event takes place at Apple, Building 4, Town Hall on March 17 at 10:00 a.m.