Macbooks supposedly contain FPGA chips (Google around but it's mentioned for example here [1] go to "step 13"). I was trying to look into it a while back but I don't think I ever got some definite answers as to what they are used for.
FPGAs aren't particularly hard to find in the PC ecosystem, especially on first-gen parts or custom jobs like Apple machines. I've seen some SSD and RAID controllers ship as FPGAs, and some sound cards bundling them for DSP use. They're usually not reprogrammable.
[1] http://www.ifixit.com/Teardown/MacBook+Pro+15-Inch+Unibody+M...