Here's an overdrive I stumbled across while browsing the Free Information Society site. It was designed by Jake Nagy and was quite popular in the DIY world at while back. Here's what he had to say about it:
Blue Magic is a very low to medium grit, tube-like, overdrive pedal
that is based on a MOSFET (BS170) pushing a JFET (J201) into
distortion. Voltage at the JFET drain should be about 4.7, but tune by
ear. [The 22k resistor] smooths out the sound, but at the cost of
sounding less “open.” Thus, reduce [it] for a more open sound. Also, experiment with the coupling
caps and the source bypass caps.
I've increased the power filter cap and added polarity protection. You can board mount pots using right angle PCB mount pots from the solder-side of the board.