Here's another one. It looks like a solenoid of sorts, it's on the same bracket as the purge control solenoid valve, shown here: You can kind of see both in this photo, again mounted on the driver side strut tower but on the side closest to the motor (right next to where the positive battery cable is passing over). The one I'm wanting to know about has the black cylinder on top of it.
Didn't know what it was for, but Toyota uses a bunch of very similar looking switching valves all over. It seemed obvious from design, though of course I couldn't tell you what it's switching FOR.