Apple has just dropped the sixth (6th!) update to their iPhone SDK and 2.0 beta firmware. Pre-req is Apple's almost simultaneously dropped OS X Leopard update, 10.5.3, so developers are forewarned to get that first before beginning the SDK install.
No word yet on what new treasures may be hiding in this version, but if past betas are any indication, there'll no doubt be something hidden in them there strings
According to TUAW, however, Apple is now carding. Yup, they're checking Application IDs at the door, so make sure you're registered before you try to install apps on a test iPhone.