skyjumper:
4) Use a buffer like a 74LCX125.
Advantages: Very cheap (the TI version is $0.08 each each line), all 4 signals can be handled by one chip
Disadvantages: ??.
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.I read the data sheet and didn't see how that works...
Oh wait, I get it. Its can be powered by a wide range of voltage and all it does is turn on and off whatever voltage is tied to Vcc. So I would need two of them. To go from 5V to 3.3V I hook 3.3V up to Vcc, tie the OE pins to ground and then attach the 5V signal lines, and that switches on and off the 3.3V output. To go the other way I just do the same thing the other way with a different chip.