This is an quite old project I made in 1996 but still interesting. It´s an simple RDS decoder based on TDA7330B RDS demodulator and AT90S2313 (obsolete part, replace with Atmel ATtiny2313) controller. The RDS data is displayed on an 2x16 character LCD. It shows program service name, RDS clock, TA flag status and scrolling 64 characters long radio text. The decoder needs an Stereo multiplex signal as input which is normally found at the input pin of an Stereo decoder IC in many radios.
Source code is available in assembler, I will make a C version some day. Decoding of the RDS data stream is based on Motorola´s "AN460 - RDS decoder using the MC68HC05", see this document for details.