As I usually print directly from the PC, I do not really depend on having a display controller attached to my Prusa i3. However I do like to have a display, because it is quite convenient to be able to control the printer off-line, to adjust the print rate while printing, or just to check the temperatures while cooling down after the PC has already been switched off.
The often used 2004 smart and the full graphics display controllers are rather large, they occupy with their two 10-pin cables a lot of the unused pins (especially on Sanguinulolu, which only has a few of those) and their backlight LEDs draw quite a lot of current from the 5V supply.
So when I first saw one of these tiny OLED 128x64 I2C displays, I thought that these were just what I needed to build a a simple DIY display controller: it is much smaller, uses less pins and draws less current and - since it also works on 3.3V! - it can also be used with the Arduino Due. The result is the tinyOLED display controller which is described with all technical details in the RepRap forum.
This project here presents printable frames for the 0.96" and 1.3" versions of the 128x64 I2C OLED displays, both available for a few dollars on eBay. Both versions use the same PCB and the frames only differ in the cutout for the active area of the display. In its simplest configuration, the controller only needs an 8-wire connection to the RAMPS or the Sanguinololu (or just 7, if you don't need the audible click from the buzzer). If desired or required, a standard microSD-card module (less than 2$) can be plugged into the read of the PCB, which requires 4 more connection wires.
The files provided with this project include the SCAD source as well as STLs of the frames for the 0.96" and 1.30" display versions and the tinyOLED PCB version 1.3. Also contained are the STLs for a snap-in rear cover and a knob for the rotary encoder. For completeness I also included the PCB layout. Note that the PCB also allows for an optional 24Cxxx type EEPROM, which might be useful for Arduino Due users.
The tinyOLED frame is compatible with the same double hinge mechanism that I already used in my frames for the Smart 2004 LCD and the Full Graphic 12864 LCD controllers. So for more details about assembling the hinge mechanism, please look there. If you fixed mounting, use M4 screw that a fit the M4 nyloc nuts which must be inserted into the the nut traps which you will use for mounting. In addition to the left and right mounting nuts, there it is also possible to use a central mount on the bottom. Be carful with the central bottom mount not to use too long screw, as this could cause shorts and damage the electronics.
Update 2015-05-08: I have now uploaded a new version of the TinyOLED display frame which has the rotary encoder mounted on the side, which results in a more compact frame and a more intuitive use.
The frames were printed from 3mm ABS filament on my DIY Prusa i3 using a 0.4mm nozzle with 0.56mm extrusion width and 0.252 layer height. I print on a clear mirror without Kapton tape but thoroughly cleaned with acetone and double concentrated lemon juice.