westfw:
I need to read in with Analog pins, and these pin don't provide interrupts.
it looks to me like the analog pins (if configured for digital IO) support the same pin-change interrupts as the other general purpose digital pins.
Do you have an I2C bus already in use? Is I2C going to be fast enough?
Yes, I have 3 arduinos talking to each other at the moment, SD21 servo controller and few other things. I2C is my choice for this matter.
Ok, I consider Mega1280 which is lying in my table, but it was too big. Features of 1280 was more than enough, but the size.
Pin-change interrupts are far away from my knowledge, I just started less than a year ago, C-language is still a mystery for me. 
If only I knew how to get the information that A0-A7 has changed state.
Cheers,
Kari