Nicholas C. Lewis is developing an interesting Kickstarter project known as the InkShield.
This shield allows you to connect a HP C6602 inkjet cartridge to your Arduino turning it into a 96dpi print platform. It only uses 5 pins which can be jumper selected to avoid other shields. It is designed with a Arduino Mega footprint but fully supports both the Arduino and the Arduino Mega. It is designed with all through-hole components to make assembly easy even for beginners.
The project is mostly funded and it looks like Nicholas has done a lot of work on this design, including an on-board 18.5V boost converter for the Inkjet head. He states that all hardware and software code will be released when the initial production run is completed.