Had the same problem myself, very little available in terms of good quality code for free, though you could have a look at the Epson web site for example code for the 1374 (for example) series controllers.
Am writing libraries for Dragonball VZ328 lcd controller at present, which uses a dumb frame buffer in system memory. Monochrome only, no greyscale at the mo, but have the low level device driver function library done to plot pixel, line, fill area and bitmap icon, as well as libraries built on top of this to do graphics primitives and text output / font select etc. All written in C and should be fairly portable.
What exactly are you looking for ?...
Chris