dsPIC Audio Processor
The smallest dsPIC with an interface for a codec is the dsPIC30F4013, which conveniently comes in a DIL-40 package option, making construction easy. I have used it with the SI3000 codec in this application. That is the chip used on Microchip's dsPICDEM 1.1 development board, and plenty of software is available for it.
Schematic:
I designed a simple single-sided PCB for the unit, and had some boards made. Here is an image of the PCB layout, from the PCB layout software I use:
Wire links on the top of the board are red.
Here are photos of the assembled unit and the PCB bottom layer:
The codec is only available in a SOIC package, and therefore had to be mounted on the underside of the PCB.
The schematic in PDF form is here.
I've formed a Yahoo group devoted to dsPIC radio applications, with more information on this board, including ordering details: http://groups.yahoo.com/group/radio_dspic/.