I haven't bought the Due yet, but 3.3 volts is not a common voltage. A lot of ICs run off of 5 volts. I googled 3.3v to 5v convertor & read about a logic shifter.
Its a very common voltage. In fact nearly all new logic chips support it. 5V is becoming
"legacy". Most Arduinos use chips that can run between 1.8 and 5V, although most
are actually used at 5V. Many sensors are 3.3 and 5V compatible and many are 1.8 to 3.6V
only nowadays. All mobile phones use 3.3 as the bus voltage these days so that all the
new chips destined for phones (like gyros, accelerometers, light sensors, magnetometers,
etc etc) are 3.3V compatible, and of course SD and microSD cards are 3.3V or below.
I'm talking about chips released in the last decade of course, not prehistory
BTW its "level shifter", not "logic shifter". These are readily available on breakout
boards and many simple circuits can perform the same function.