The VEX robotic system is being sold at Radio Shack(tm) for 50% off or more at the time of this wrighting, that's $150
it's a nice kit for $150, the radio and reciever are worth that alone. Pick up the programming kit for $49, then you can load your own code into the module instead of using their canned routines. The rechargable battery pack is worth the additional $25.

Several RG members now own the VEX kits.

Hardware info:
The default kits are channel 61 75.41 mhz and appear to be ordinary R/C-ground crystals. 

Radio:
The radio has 2 sticks (4 analog channels) and 2 sets of buttons to control 2 other channels. The servo is centered when the buttons are unpushed, and the buttons simulate stick up/stick down condition.
There is a controller in the radio and it has some programmability for combining, reversing, and trimming the control.
There is a 4 pin connector on it which someone says has this pinout:
Pin 1 = +5V
Pin 2 = Data
Pin 3 = GND
Pin 4 = Tether detect. (shorting this to GND, on the transmitter, blocks the transmitter, from another msg.
showing how to wire a multi-pole single through switch to control competitions.)
Data is in a solid stream, of single digits, 0 to 255... dont know the info

Receiver:
The receiver has an antenna and a 4 pin jack that connects it to the controller brain.
It converts the RF 6 channel into serial. It contains a ta31136 FM receiver and something that might
be a ta75W393FU dual comparator.  I guess it is just demodulating the rf and the processor is responsible
for breaking out the 6 channels of RC pusles. 

Controller Brain:
The controller has jacks for serial port and 2 receiver ports so you can have 2 separate controllers (12 channel R/C).
The VEX robot controller contains 2 pic18f8520 chips. One is labled "user" and the other "master". They share a 10mhz crystal. Among other components are a lm294 5v regulator and a smaller 2931A 8pin soic (probably a 3.3v regulator). There are 5 LEDs (one glows through a red slit over the other 4 but it is not an IR port).  A ULN2003A (seven darlington
drivers) chip is found near the servo motor outputs. 

The 16 Analog/Digital 3 pin ports read 0=ground 1=+5v 2=input/output. Pin 0 is the one closest to the edge of the case and pin 2 is inwards. The jumpers have 3 pins but the center pin is no contact. So they act as switches to ground the weak pullup input.

The motor outputs appear to be:
Pin 0 (outer edge pin) to black wire = ground 
Pin 1 (center) to orange wire = +7-8volt from battery.
Pin 2 (closest inward) to white wire = signal.

Servos/Motors
The servo signal is standard 1.5ms servo center/motor stopped and occur about every 17ms.
They seem to be good and powerful and a good deal at the 1/2 off price. 
They include a servo saver clutch and extra gears.
The hardware is nonstandard for servos, it has two mounting screw holes on top and a hole for a square drive shaft instead of the plastic arm that servos usually have. This may be quite useful for certain types of wheel mounting, but note that the square shaft is not secured to the servo, I guess you could glue it if doing non VEX hardware.
White wire=signal, Orange=+ 6 to 7.2v, Black=GND

Ultrasonic Range Sensor:
It was commented on the web that this is a Daventech SRF-04 so its a good deal at the 1/2 off price. I dont know if the quality is as good as the parallax ping. If it is a Daventech then this info should be valid:
Voltage: 5V only Required 
Current: 30 mA Typical, 50 mA Max. 
Frequency: 40 KHz 
Maximum Range: 3 meters (~10 ft.) 
Minimum Range: 3 cm (~1") 
Sensitivity: Detect 3 cm dia. broom handle at > 2 m 
Input Trigger: 10 uSec min. TTL level pulse 
Output Pulse: 10uS to 18mS ~36mS if no object detected, wait 10mS before next pulse
Note it has lables input and output but from what I have read, those are from the reference of the vex controller. You send a pulse to its "Output" line and get the signal back from its "Input" line.
Timing diagram: http://www.junun.org/MarkIII/datasheets/SRF04_timing.pdf


The basic project given, "squarebot" is a good start
to test the kit and is supprisingly powerful for the
little servos running on a fully charged nicd pack.
Its downfall is a drive gear that barely doesnt touch the ground (level floor only)

Programming Kit:
The programming kit contains a USB to RS232 port, a RS232 programming module that connects to the controller to reflash it. It is not a simple breakout. It contains a RS232 level shifter and a small PIC12 controller. It is likely possible to find a way to reprogram the device without the kit but it may involve board modifications. There are discussions on this but any real info is suppressed. Most likely if you want to program or use any of the advanced sensors then you have to buy the programming kit. It comes with easyC, and you may be able to program in PIC assembly but thats unclear. 

I have yet to google up a treasure of VEX info beyond their site and the first competition site, though this kit been out for some time now so you would expect to see web rings and a plethora of hacker info out there. The info I have found to date on easyC or using other languages like PIC assembly is minimal. It's unclear to me what the interaction is between the master and slave PICs in the controller or how to use the interrupts. 
As we learn new things or write code, it can be posted here.
- GrayMack