Available: Now. Easy to find online, hard in stores except Lego stores (I hear). Released in August 2006 I believe.
Price: about $250
Requires: 6 x AA batteries (sold seperately), USB or Bluetooth connectivity (PC/Mac)
Official Site: LEGO Store - LEGO® MINDSTORMS® NXT

It's a 2nd generation (AFAIK) build and program your own robot kit from lego

Features / Specifications

• All-new NXT Intelligent Brick with 32-bit microprocessor, more memory and FLASH
• 3 Interactive Servo motors feature built-in rotation sensors to align speed for precise control
• New sound sensor reacts to sound commands, patterns and tones
• New ultrasonic visual sensor responds to movement
• Improved touch sensor reacts to touch and release
• Improved light sensor detects different colors and light intensities
• 519 specially selected LEGO TECHNIC elements for sturdy and durable building and improved functionality and movement
• 4 input ports, 3 output ports and 7 6-wire cords
• Matrix display
• Real sound speaker
• USB 2.0 and Bluetooth support
• Easy-to-use PC and Mac compatible interface
• Intuitive, icon-based drag-and-drop program "building" environment

Pictures


The inside cover of the box, showing the contents. Mine was slightly beat up when it arrived, but overall it came in decent shape.



The cat's been very curious the last few days. She's not really scared of it, but very interested.


Here's all the stuff unpacked with my first robot in the background.

There are lots of little parts and at first it's a little bit intimidating putting them together. I read the manual (~70 pages) so I understood what all the sensors and things do. There's a "get started" pack that lets you begin building your first bot right away. You'll need 6 AA batteries to power the bot. I found an 8-pack of Energizer 2500mAh batteries that charge in 15 minutes at Best Buy for about $25. So far I haven't had to charge the batteries yet.

There are four sensors (light, distance, sound, and touch) and three motors. On the NXT box (the brains of the unit, where USB/bluetooth and all the sensors/motors connect) you can write programs directly. Or if you prefer you can use the Windows/Mac software to program in a GUI environment that's very easy to use. Also built into the NXT unit is a sensor test and demo (which is used for the first basic robot).

You hook up the four sensors to the bottom of the unit with what looks like a phone cable. All the cables are interchangeable and there are enough to use everything the kit includes simultaneously. The sensor test takes only a few minutes and is very interesting. The first port connects the touch sensor. When it's connected and the test is run, a Lego head says "Whoops!" when you touch the sensor and the screen indicates a binary value of "1" has been assigned because the sensor is activated. When it's released the number goes back to "0".

The second sensor connects the microphone which can sense the difference between human and non-human sounds (to a point) by measuring the decibals differently for a person. The value is indicated on the screen, from 0 to 100, 100 being the loudest. The third port uses the light sensor (which so far for me hasn't seemed too accurate in determining color). It also has an output light to measure reflective properties of a surface. The sensor can detect direct and ambient light accurately. Finally, the fourth sensor is the Supersonic sensor, which functions like a bad's radar. This is the unit that looks like the eyes of the robot (similar to Johnny 5's Head). It bounces two soundwaves across the room and takes the reflection to determine how far it is from an object. It's very accurate! I tested it within 1cm accurately. It could also be used to determine how fast an object was moving with some clever programming.

The first bot took me about an hour to build, screwing around and getting an idea of how it all worked together.

It doesn't do much at this stage, mostly drives around and makes basic turns. Then it was time for upgrades...


Here's the bot flipped over, so you can see its rear wheel is just a standard spinning disc made from basic Technic pieces. The front wheels do well on carpet and the three motors have ample power. The phone cables that power the motors can be seen here.


Johnny 5's head, the supersonic sensor that resembles a bat's radar system.


The NXT control brick. At the top you'll see the ports A, B, C, which control the motors. They all function the same, but to keep things standard, you'll usually use B and C for primary movement and A for other features. At least that's how it's been so far with the TriBot and arm. You can change which motor is controlled by which port by telling the program what motor to turn at what time, etc.


This is the back of the light sensor. Here you can see the female end of the phone cord style connector.


This is the assembled and completed Tri-Bot. Including the other steps, it took me about an hour and a half on my first attempt to work out all the bugs. From the last image, you'll notice it now has claws in front. These are controlled by the third motor. It rotates a pair of gears underneath forward or back, which controls opening and closing of the claws. The white sensor aiming directly at the floor (at the base of the arms) is the light sensor. It's used to determine what color the surface is underneath it. On the test pad there is a black circle and the bot is programmed to stop when it sees black, so it doesn't leave the pad.

The sound sensor is mounted up top behind the NXT brick. Its purpose is to gather sounds for commands. In the first program where you use it, the bot waits for your command (any word at 50%+ volume to the microphone) before grabbing the ball.. The supersonic sensor in front (that looks like its head) is used to determine how far away the object is. Your first program with it will require you to set the ball with 15 inches I believe, at which time the robot charges forward and waits for your voice to grab the ball. It can be pretty scary when the bot drives forward! If it misses the ball, it won't stop until it crashes its sensor into something. Hanging directly down from the head is a bar that swivels when it runs into something. As it swivels downward, it makes contact with the touch sensor, which informs the NXT box that the sensor has been triggered.


Here's the tri-bot ready to charge for its ball.


The back of the Tri-Bot. You can see how the NXT brick connects to the various components and get a good glimse of the rear wheel. Notice how the cables are rather bulky and look like they'd get in the way -- they don't. The bot can typically be built to allow freedom of motion regardless of the cable length.

The Tri-Bot is really cool but it has one major downside, at least for me. The whole front area: the head, claws, touch sensor and light are held on by two very short vertical pegs, directly in front of the NXT brick. Since they're so short, they separated when the bot made a fast movement like grabbing the ball. Slowing down the motor's speed would probably help (which is very easy in software), but the default values caused my Tri-Bot to break here often.


The second bot, about 1/2 way through the build. It's eventually going to be a crane that moves an arm, then lowers and closes the arm from what I gather. Currently it simply moves back and forth, up and down. You may notice the black cranks next to the front motors. These are very fun to watch as the motor spins to life. Also you can manually move the crane using these.


Top view of the crane so far. You can read "First Program / Run" from the NXT brick. It has a simple operating system for choosing what files and sounds to play, as well as full programmability. I hate one thing about it, though. The orange button sticks often. If you don't push it perfectly, since it's rubber and flexible, it gets hung up on the plastic casing. Take a careful look at the black gears. These things fit together like magic. As you reach this stage of the assembly, it's hard not to admire Lego engineers for their job well done.


The side view of the crane. Everything from the front part, wrapping around toward the back is currently not functional and only holds the crane off the ground. The somewhat complicated structure of the crane is visible here.

To Come Later
I am still working on getting the videos online. I'll post screenshots of the programming interface as well. Also I've barely scratched the surface with this bot, so expect lots of crazy bots before I'm tired of it.

Eventually I'll post recommendations on how to organize the kit if you should buy it, because it's not very fun digging around in a bin for pieces this intricate.

My Thoughts
I firmly believe that this is going to be THE toy to have this year. It is well worth the money for a strictly educational sense. This makes learning about robotics, engineering, and programming very fun. I've had a blast with it so far and I imagine some of my creations will be much more interesting. There are bot that walk, one that rolls on a single wheel (like a unicycle) using the light to balance, a cuckoo-clock, nd many more interesting projects out there.

If $225-$290 is up your alley for a neat toy that will likely bring hundreds of hours of entertainment, this is a very solid BUY recommendation. Now if only I could teach it to handle a laser gun...

Links
NXT Repository
Mindstorms Revolution
Wikipedia Entry
Ars Technica Review (10 / 10)
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I got it for $224 shipped which is about $70 less than Lego wanted.