Attaching 3.5" desktop drive to MacBook SATA
Just an update - I've successfully connected my 2TB HD to my MacBook's internal SATA data connector. If anyone's interested in doing this themselves, you'll need:


external enclosure with eSATA to power the drive (I'm using a NexStar CX with eSata):





an eSATA to female SATA cable (I got mine from http://satacables.com, see "eSATA DATA Cable Extension Male to Female" near the bottom of the page):





You'll need to cut those plastic tabs off the SATA portion of the cable, leaving only the section with the pins - otherwise, the cable won't fit in the port.
Follow iFixit's steps for removing the keyboard section of the MacBook 
Remove the hard drive, connect cable. Since we had to remove the tabs on the cable in order to make the connection, the cable does not latch in place. I recomment taping the table to the bottom of the case where the hard drive was:


Reverse the disassembly steps to put the computer back together, with the exception of the memory cover and the battery. The cable should now poke out of the hole where the battery used to be.
Install the hard drive in the external enclosure, connect the eSATA and power cables, and enjoy.