With typical Power Consumption of about 5mA when active at 16MHz, 9v battery of 150mAh capacity.
it will be 150mAh/5mA about 30 hours.

You may ref some of the code here for the Gyro and accelerometer.
http://code.google.com/p/arducopter/

http://www.starlino.com/imu_guide.html
http://www.instructables.com/id/Accelerometer-Gyro-Tutorial/

The MOSFET need to operate higher then 9V.

You may try this...
IC H-BRIDGE 5A DC MOTOR TO220-7 - TLE5206-2

http://parts.digikey.com/1/parts/577889-ic-h-bridge-5a-dc-motor-to220-7-tle5206-2.html
http://support.technologicalarts.ca/docs/NanoCore12/SSMI/tle5206-2_20010619.pdf

Base on the datasheets if operate 1MHz 1.8V it draw 300 micro Amps. so if you operate at 3.3V map be about 1mA.

Please read the section 7 on power consumption issues. like disable ADC, all port pins was avoid unconnected, have a defined level. Connecting unused pins directly to VCC or GND is not recommended, since this may cause excessive currents if the pin is accidentally configured as an output.

You may take a look on this "Pololu 3pi Robot"
http://www.pololu.com/catalog/product/975

The 3pi used ATmega328P and is compatible with the Arduino development platform.

http://wn.com/Binary_Clock_using_the_Arduino

You have connected your potentiometer may be the center pin to Grd so when you turn the pot it resistance too low therefore smoke came up around the potentiometer. I thought the Arduino Duemilanove has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent. Why it not working? :o

Check out this Site, they make similar circuit.

https://randomskk.net/projects/lightstrip/schematic.pdf

Arduino: microphone input

http://student-kmt.hku.nl/~arne0/x/arduino_input_microphone.zip

I came a cross mouse with 3-pin photo detector,  1 pin go to ground,  middle pin to +5V and the other pin connected to input of device without resistor. You may try it out.

Follow this tutorial and using the AVR Studio 4 to change Fuse Settings
http://www.arduino.cc/playground/Learning/Burn168

L4940V5 Low Drop Voltage Regulators/Drivers 5.0V 1.5A Positive
Dropout Voltage (Max):      0.4 V @ 500 mA
1.5 A current
0.5 V dropout at 1.5A (0.2V at 0.5A)
reverse polarity protection
thermal shutdown
for Qty 10:       @USD $1.69

http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsGz1a6aV8DcGTYtsLlapNOlJJElQme%252bK4%3d

programing ADC to measure resistance
To measure a resistance you need to use Ohm's Law (E = I*R or R = E/I). So, apply a constant current (I) through the resistor and use the ADC to measure the voltage across the resistor then calculate the resistance.
Google will find tons of information on this.

This a post back in 2008 and it work.
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1216381158/all