Earlier, I posted this topic on the schematics page but now the design is pretty much finalized so I am going to post the final schematic here:
(http://circuitsaladdotcom.files.wordpress.com/2013/06/simple-ring-modulator1.gif)
There is lots more technical info and a link to the PCB board at www.circuitsalad.com
One very important feature of the design is the elimination of modulation leakage because of the opto-coupling of the modulation signal. Also, many other OP amps will work in place of the TS922.
The MAX 7410 is an adjustable from 1Hz-15KHz, 5 pole, low pass filter. While it is somewhat exotic, it provides some really nice filter effects for the modulator.
When using very low modulation frequency and sweep the low pass filter - you end up with a phaser like sound from all the phase shifting that occurs in the filter and the mixer.
here is a demo of the pedal built in a 1590BB enclosure: