Dan East
A first port of the excellent Adafruit ST7735 library Also supports the S6D02A1 controller (Use 1k resistors in series on all logic lines).
Fork of
Adafruit_ST7735
by 
Andrew Lindsay
Modified version of the ST7735 library to support the Samsung S6D02A1 controller. These 1.8" 128x160 displays can be purchased dirt cheap (under $5 on eBay or aliexpress with free shipping).
You must also import the Adafruit_GFX library, as this library is dependent upon it.
I've used up to 20 MHz SPI with no problem. That is hardcoded in the library, and is currently set to 4 MHz (unmodified from the original library).
The library is exactly the same for S6D02A1 and ST7735 except for the initialization routines.
Use 1k resistors in series on all 5 logic lines as 3V3 is required (display is not damaged by 5V logic, but it will not work)
Constructor pin names that match the S6D02A1: Adafruit_ST7735(DIN, NC, CLK, CD, D/C, RST) ;
Source of initialization codes for the S6D02A1: https://github.com/zigwart/Adafruit_QDTech/blob/master/Adafruit_QDTech.cpp