Gizmodo and GearLive are reporting that the iPhone 2.0 firmware will go golden master (locked for shipping) this week. Golden master does not necessarily mean that Apple will ship the firmware this week (after all, Steve said that it would ship in "early July") but it does mean that the firmware and all the features are complete and ready to head out the door.
Both sites seem to agree with the build number on the new firmware: 345. Gizmodo is reporting that 2.0 will boast code signing and a new encryption feature. The iPhone firmware 2.0 is definitely something on every iPhone owner's wishlist, and here's mine (you have one of these, right?):