> If you use PWM to drive the LEDs you may not need current-
> limiting resistors. Adjust the duty cycle to suit the supply voltage
I wouldn't do this for the intial prototype. If the code hangs or you 
are single stepping with a debugger you don't want the LEDs driven 
beyond thier continuous maximum. Maybe do this later if you want to get 
a bit more efficiancy or brightness out of the system and are confident 
that your code is solid.

Another problem is consistancy. The brightness for a given current is 
usually fairly constant. The relationship between current and voltage is 
not. So a slightly higher input voltage with a series resistor while 
giving lower efficiancy should give much better consistancy between then 
LEDs in the array.
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