Since last night 1AM Singapore time, Apple's 3.0 update for the iPhone OS is available. While I haven't updated it yet (I was asleep, and after waking up went to work ), others already tried it successfully.

An overview of the newest features and a guide on how to install the update can be found on Apple's website.

Also, there's an interesting article that explains "How To Use The Best 40 Features of iPhone 3.0".