Apple has scheduled a press event on March 17th to show off features of iPhone OS 3.0. Details are scarce, but it's safe to assume significant enhancements will be announced. Release of the third generation iPhone is expected in June, and it's anticipated that iPhone OS 3.0 will be released at the same time.
The iPhone 3.0 press event is scheduled for 10 AM PST in the Town Hall auditorium at Apple's Cupertino campus.