Core 2 comes in many flavors:
Merom - mobile CPU, 667 MHz FSB, 2/4MB L2, ≤ 2.33GHz -> iMac
Conroe - desktop CPU, 1066 MHz FSB*, 2/4MB L2, ≤ 2.67 GHz** -> not (currently) used by Apple
Woodcrest - workstation/server CPU, 1333 MHZ FSB***, 4MB L2, ≤ 3.0 GHz-> Mac Pro, Xserve
*) in Q4 Intel will introduce the E4200 Allendale with only an 800MHz FSB. Other than that one, all Conroes have a 1066 MHz FSB. The rumored X8000 Conroe Extreme supposedly has a 1333 MHz FSB, but that won't materialize until the end of the year.
**) The Core 2 Extreme X6800 also offers 2.93, an X6900 with 3.2 GHz is expected by the end of 2006.
***) There are two low-end Woodcrests (5110, 5120) that use a 1066 MHz FSB, but Apple doesn't use them.