Anyone interested running Arduino (generic) code, or using Arduino libraries (like Adafruit) on LPC13xx (or almost any other LPC), check this out: Arduino-XC - LPC1347
Very usable (UART, SPI, I2C, half a dozen of Adafruit libraries: ADXL345, BMP085, GFX/LCD, ST7735, TCS34725, LSM303) but still under heavy development.