I know there are like four or five other libraries out there for this, but all but one of them are fairly non-comprehensive (or outdated) and the most recent one I didn't find out about until I was quite some time into writing my own. So, I present to you, 4Duino. There are a few joystick/sound/raw-image-drawing functions not yet covered, but otherwise the entire GOLDELOX SGC API is covered.
* currently officially supports GOLDELOX <256px devices (I've been testing on the 96px display)
+ NEW - PICASO support is coming along, and most basic functions should now work seamlessly with PICASO displays! Should be safe to use, but I'd recommend updating your device first!
* SD commands supported
* supports both hardware and software serial; only gotcha is you have to #include "SoftwareSerial.h" whether you're using it or not.
* documentation/API reference.
* more custom widgets (ProgressBar currently implemented)
* more example sketches (Mystify and ambient light control examples included currently)
* missing functions (joystick/sound/raw-image-drawing)
* universal (> 255px, touch, PICASO controller) device support
(when I can afford one of the larger screens).
+ See above, PICASO support is coming along nicely.https://github.com/planetarian/4Duino