Hello, i found a good family here in http://www.diydrones.com/, is an excellent group of people trying to build an automatic airplane like me, they are helping me with the Arduino automatic pilot and the translation stuff. :
Info and source code here:
http://www.diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A19829
Don't forget read the comments, i explained a litte bit more about Kalman Filters.
Jordi 
That's really impressive code, Jordi. Since you are putting this into a heli, are you planning to make a single PCB to hold down weight? Perhaps a socketed ATmega168 and your sensors, nothing else?
Yes maybe, or perhaps a simple PCB with mini arduino slots on it. ;D I possible to use the same crystal for two atmegas168?
possible to use the same crystal for two atmegas168?
Crystal? I don't think so.
A TTL crystal oscillator, however, is a different story. With careful board layout you may be able to drive multiple inputs with an oscillator.
That will probably require fuse changes, though.
-j
Yes the crystal oscillator (16mhz), CAN I USE one crystal for two atmegas 168??? :-/
OK here is the final version of the ArduIMU.
Video:
-Yellow color = Just Accelerometer read
-Red color= Accelerometer+Gyro+KalmanFIiter
Arduino Source Code:
http://jordii07.googlepages.com/ArduIMUFinal.txt
Labview (ground station) source code:
http://jordii07.googlepages.com/IMUfinal.llb
I configured Arduino to externally adjust the accelerometer jitter filter and the gyro rate, using the nunchuck potentiometers (joystick axis). Now is working pretty well.
To do:
-Integrate another Gyro (to make it dual axis).
-A bank robbery, to buy all the components i need.
-Program the SPI altimeter
-And put all the hardware together and make it work (gps, altimeter, IMU, modem).
-Making a PSP program to read serial data (using psp uart port). : to make a portable ground station. (but this is a secret)