There have been some rumblings that iPhone OS 3.0, scheduled for release today, is actually coming out tomorrow. Don't panic! It'll still come out midday today, so long as you don't live in East Asia.
The confusion can be traced to Apple's Singapore site, which clearly sets the release for tomorrow. Thing is, Singapore is 13 hours ahead EST, and a full 16 hours ahead of PST. In other words, if firmware 3.0 shows up at noon in NY, it'll be showing up tomorrow in Singapore, Japan, Australia, etc.
So, since Apple's American site still shows the expected June 17th release date, that means we probably won't see firmware propagate through iTunes until noon or after, EST. There is a 3.0 image hosted on Apple's servers, but it's apparently for the 3GS exclusively, which isn't much help to anyone: it won't work on your iPhone 3G, and if you somehow already have your 3GS, then, well, you've also got 3.0.
More on iPhone OS 3.0 here.
UPDATE: Reader Chris has coded together a clever little script that monitors Apple's download servers. If you feel the need to refresh something all day, make it this. [TechCrunch, Register—Thanks, Kirk and Julie!]