The large chip is the
Broadcom BCM2042, which provides not only Bluetooth connectivity but also serves as the processors with built-in RAM/ROM memory.
Below and to the right of the large Broadcom chip is the
SST25WF020, which provides 2Mbit of serial flash memory.
Above and to the right of the large chip is the Broadcom BCM5974 touchscreen controller. This is the same chip found in other Apple devices that support Multi-Touch, like the MacBook Pro.
Above the large Broadcom chip is a Texas Instruments chip with markings CD3238 TI 01J P20T.
Photo credit: Bill Detwiler / TechRepublic