ThinkSecret points to channel reports indicating that Apple may be preparing for "at least one" product announcement this Tuesday, September 5th, 2006, but were unable to specify which models would see updates.
Meanwhile, more confident reports have pointed to iMac updates on September 12th.
Finally, independent but unconfirmed reports claim that the MacBook will receive quiet speed bumps later this month (Sept 25th), but no word on whether or not the Core 2 Duo would be used.