I recently got a Nokia 5110 48 x 84 LCD display from ebay. I looked at the driver's datasheet http://www.sparkfun.com/datasheets/LCD/Monochrome/Nokia5110.pdf , and it said that the maximum operating voltage is 7v, but some people say that it only works with 3.3v. Is it okay to wire it directly to a 5v arduino nano?
Datasheet page 3:
Logic supply voltage range VDD to VSS: 2.7 to 3.3 V
I'd say that's a no.
Use level converters.
It doesn't matter how official that manual is - it's just confusing gobbledegook. The best advice seems to be to power the device with 3.3 and, if you've got 3.3v available, why not use it?
I find all the other connections can be made direct - no level shifting or resistors.