Here is a fine piece of technical art, Coyote-1 from Howler Audio. It is an open source guitar effect box which comes with a full hardware and software documentation, so guitarists with a programming talent can write their own DSP code to perform effects that are new to us. A small Windows utility helps to organize effect patches in the desired order. The box has a Propeller DSP from Parallax, there are eight cores inside, all running at 80 MHz. It has a high-level programming language, Spin, and of course you can reach the cores with assembly instructions, too. A direct video output is also present from the processor itself, so you can connect a video monitor. Check here for more details.