Digital Audio Effects Design
If you are interested in what is being used in commercial designs, I have here an Electro-harmonix Memory Man. It uses an Analog Devices BlackFin ADSP-BF531 with an ISSI 42s16800 RAM chip. They're using a CS4272 converter and 33078 op amps to get the signal in and out, and an ADC108S022 which is probably used to digitise the various pots. That's it apart from power supply components.