Whats the fastest micro-controller that pretty much cab be programmed similar to an arduino out there that can operate sensors e.t.c?
check teensy family or the due
there are also fun processors like mbed.org
Also look at the Chipkit uC32, which uses an 80 Mhz PIC32, I believe. Has an Arduino- UNO form-factor. Not an ATmega, but uses the MP-IDE Arduino-compatible multi- platform IDE. 80 Mhz and 32-bits is pretty fast.
If you're prepared to use C#, the latest netduino is apparently 168MHz.