Following my post on the Bus Pirate,here I write about an SPI to UART converter,built using the MSP430 Launchpad.A very useful application for testing new chips or devices,which use SPI.
More on that,here . Do take note of the bug fixes mentioned on the page,before compiling it.This was originally written in mspgcc,but users have ported it to CCS as well.
I have used this successfully on many occasions,to interface with my Ethernet module,and a CMOS Flash Memory chip I recently came across.Flawless :)
A similar device is the I2C explorer,documented here.
These are must have tools for any embedded systems enthusiast.