print data after being plugged back into USB I have an arduino uno powered by a battery on a buggy with a sonar distance sensor.  I have a program that calculates the speed it's going, and I want to correlate speed with stopping distance.  I can measure the stopping distance manually, but I want the arduino to report to me the speed it was going when the motor was turned off.  I don't have an LCD display - I wanted to print the number to the serial monitor, but plugging it back into the USB port resets everything I think, or at least the serial monitor.

Without buying more components, can I get the data (calculated speed) somehow?
You could have it write the final speed to EEPROM after the motor is shut-off, and output this value when the Arduino boots, see:
http://www.arduino.cc/en/Reference/EEPROM