MichaelMeissner:
If you still have pins 0 and 1 for USB serial support, in theory you could connect the phi-panel instead of the USB, and use the 20x4 terminal like you would the USB serial support. Most of the kits have the 20x4 screen, but one of them just has the just the PCB and the ATMEGA328P-PU loaded with firmware for $9 plus s/h. http://www.inmojo.com/store/liudr-arduino-and-physics-gadgets/item/serial-lcd-back-pack---phi-panel/
Thanks for mentioning my phi-panels! The added benefit of using this panel is the option to use multiple keypad layouts, such as rotary encoders, matrix keypads, and buttons, all on the serial port, besides having a serial LCD. Besides, if you ever want to fully use your ethershield, with the SD card, you will need the SD card library, at the cost of 1.5KB of arduino's 2KB RAM. You will find it much better to not use any more libraries such as an LCD library written by anyone. Phi-panel has on board menu renderer and you don't even need a menu library if you render a menu, just send plain text and magic!