The libbuspirate is a C library to talk with the bus pirate hardware (http://dangerousprototypes.com/docs/Bus_Pirate) in raw, binary scripting mode. The libbuspirate allows to quickly write a short C program to test interfacing with your favorite hardware.
The library has mainly be used to interface through SPI with RF transceivers such as CC2500, MRF24J40, ... Example code to talk with this hardware is provided in the source code.