An open source 512K SRAM memory module for adding extra ram to your project:
I have designed a very simple PCB module that allows access to 512KBytes of Static RAM. It is compatible with any microcontroller with at least 13 free digital IO pins and the ability to run from a 3.3v or 5v supply.
It uses four 128K x 8bit SRAM chips connected in parallel. This is a 4 layer board with components placed on both sides.