I burnt up my mega and don't have another one. Can I get a duemilanove to run 51 leds in a string the way the mega would have? This is my 1st project so stay simple with any advice. I'd like to use the duemilanove for inputs and patch into the mega for outputs so that there's minimal rewiring. Possible or dreaming?
Not by direct drive. Only in some sort of multiplexing or an led driver chip.
You could use an external power supply to power the LEDs and just use the Arduino to turn on/off a relay that controls them.
Can you clarify what you mean by "a string"?