Somehow, folks in Taiwan and mainland China always manage to acquire and overclock unreleased processors before everybody else. We have two culprits today: the people at IT.OC.com.tw have overclocked an Intel Core i7 sample, while one of their counterparts at the Coolaler forums has done the same with an unreleased 45nm AMD Phenom.
According to the former's CPU-Z screenshots, the Core i7 made it from its 3.2GHz stock speed all the way up to 4.2GHz. That achievement seems to have involved a substantial bump in voltage, though—CPU-Z reported 1.72V. Interestingly, CPU-Z also reported four cores and eight threads, so IT.OC.com.tw apparently didn't need to switch off Hyper-Threading to go over 4GHz. (Overclockers often turned off HT to reach higher speeds back in the Pentium 4 days.)
On the AMD side of things, Toppc at the Coolaler forums got his 45nm Phenom engineering sample from 2.2GHz to 4GHz. The AMD CPU also required a big voltage boost to make it that far, but Toppc settled for a somewhat tamer 1.6V. Pictures of the overclocker's setup show a bulky heatsink with a 120mm fan slapped on top of it, so the overclock may not have involved exotic cooling methods.
If you haven't been keeping track of the latest rumors, recent reports pinpoint November 17 as the release date for Intel's Core i7 processors. 45nm Phenoms could arrive in late December or early January, judging by the latest whispers from Asian rumor sites.