Here's a picture of the PCB layout so far:
http://picasaweb.google.com/mark.seel/NextAudioDigitalAudioSignalProcessor#5565090890081058578The board is 4 layers and is only 1.0" x 1.2" and will fit on a solderless prototype board for experimentation.
The board contains:
- 400Mhz XMOS XS1-L1 CPU
- Switching 1V regulator for CPU core
- Linear 3.3V regulator for CPU I/O
- Crystal Oscillator circuit for CPU system clock and audio master clock
- Power-on reset delay circuit for CPU
- 20-Pin DIP XTAG interface
- Two rows of 10-PIN SIP's for I/O's and/or plugging into a prototype board (20 PIN DIP with 1" DIP width)
- SPI interface for external program EEPROM
Since it hast the 20-pin XTAG connection you can use XMOS's $50 JTAG interface and the free programming IDE to compile, download, debug, and even burn the program EEPROM.
I took the CODEC and EEPROM off of the board so people can choose their own parts.
Since the EEPROM's chip select is brought out to a pin you could use the SPI bus for other peripherals without consuming other GPIO's for SPI signals (except for chip selects of course).
As mhelin pointed out there's some nice CODEC boards with stereo jacks that could be hooked up easily. Can't wait to try that out!
I still have to check for errors but it's pretty close to done.
I'll bring up a web-site soon for instructions, PCB files, hook-up examples, programming examples in the next couple of weeks.
I can build and test a board for around $30 to $40.
Sorry about the cost! Building one myself takes time (I'm not very fast at soldering SMT parts and I can't work for free!)

Or you can build it yourself - you can buy just the board for say $5.00 and reference the bill-of-materials and parts placement diagram on the website (coming soon).