The Sequential Manual Transmission is Toyota's name for their electro-hydraulically shifted manual gearbox found in the MR2 Spyder. Initially in a 5-speed but now also in a 6-speed flavor (with an extra overdrive gear), its operation is controlled by two steering-wheel-mounted buttons on the front for initiating a downshift and two on the back for initiating an upshift, as well as a more familiar floor shifter with a + to upshift when pulling toward you and a - to downshift when pushing away.
Operation is simple. The floor shifter has three gates:

   _    _
R | |_  _
  |_  || |
N   |__  | S
       |_|
         +

To start the car, the selector must be in the middle, neutral gate. After started, it may be placed in rear or drive which will cause the gear to shift but not the clutch to be dropped. The car will not creep like an automatic, only roll like a regular manual with the clutch out! Giving it some accelerator, the clutch will slowly slip and engage and you will be in gear.
To upshift, lift the throttle slightly to ensure smoothness while shifting and the car will slowly (albeit not too slowly to be disruptive) upshift, very smoothly. To downshift, just hit the button and it will double-clutch like a pro, both quickly and smoothly!
Coming to a stop, the computer will downshift to first gear for you and disengage the clutch. One nicety about this transmission is that it is generally impossible to stall, except for if you spin out, so you'll likely never need to worry about it :) It may not be as finely-executed as BMW's new SMG transmissions, but for a mere fraction of the price it's a very convenient, useful, and fun bit of new technology!